.TH DDPT "8" "April 2014" "ddpt\-0.94" DDPT
.SH NAME
ddpt \- copies data between files and storage devices. Support for
devices that understand the SCSI command set.
.SH SYNOPSIS
.B ddpt
[\fIbpt=BPT[,OBPC]\fR] [\fIbs=BS\fR] [\fIcdbsz=\fR{6|10|12|16|32}]
[\fIcoe=\fR{0|1}] [\fIcoe_limit=CL\fR] [\fIconv=CONVS\fR] [\fIcount=COUNT\fR]
[\fIdelay=MS[,W_MS]\fR] [\fIibs=IBS\fR] [\fIid_usage=LIU\fR] \fIif=IFILE\fR
[\fIiflag=FLAGS\fR] [\fIintio=\fR{0|1}] [\fIiseek=SKIP\fR] [\fIito=ITO\fR]
[\fIlist_id=LID\fR] [\fIobs=OBS\fR] [\fIof=OFILE\fR] [\fIof2=OFILE2\fR]
[\fIoflag=FLAGS\fR] [\fIoseek=SEEK\fR] [\fIprio=PRIO\fR]
[\fIprotect=RDP[,WRP]\fR] [\fIretries=RETR\fR] [\fIrtf=RTF\fR]
[\fIrtype=RTYPE\fR] [\fIseek=SEEK\fR] [\fIskip=SKIP\fR] [\fIstatus=STAT\fR]
[\fIto=TO\fR] [\fIverbose=VERB\fR] [\fI\-\-help\fR] [\fI\-\-odx\fR]
[\fI\-\-verbose\fR] [\fI\-\-version\fR] [\fI\-\-wscan\fR] [\fI\-\-xcopy\fR]
.PP
For comparison here is the synopsis for GNU's dd command:
.PP
.B dd
[\fIbs=BS\fR] [\fIcbs=CBS\fR] [\fIconv=CONVS\fR] [\fIcount=COUNT\fR]
[\fIibs=IBS\fR] [\fIif=IFILE\fR] [\fIiflag=FLAGS\fR] [\fIobs=OBS\fR]
[\fIof=OFILE\fR] [\fIoflag=FLAGS\fR] [\fIseek=SEEK\fR] [\fIskip=SKIP\fR]
[\fIstatus=STAT\fR] [\fI\-\-help\fR] [\fI\-\-version\fR]
.SH DESCRIPTION
.\" Add any additional description here
.PP
Copies data between files or simply reads data from a file. This utility is
specialized for "files" that are storage devices, especially those that can
use the SCSI command sets (e.g. SATA and SAS disks). It can issue SCSI
commands in pass\-through ("pt") mode. Similar syntax and semantics to the
Unix
.B dd(1)
command.
.PP
For comparison, the SYNOPSIS section above shows both the
.B ddpt
command line options followed by GNU's
.B dd(1)
command line options. Broadly speaking ddpt can be considered a super\-set
of dd. See the section on DD DIFFERENCES for significant differences
between ddpt and dd.
.PP
This utility either does direct copies, based on read\-write sequences,
or offloaded copies. In an offloaded copy the data being copied does not
necessarily pass through the memory of the the machine originating the copy
operation; this can save a significant amount of time and lessen CPU usage.
.PP
When doing a direct copy, this utility breaks the copy into segments since
computer RAM is typically a scarce resource. First it reads in \fIBPT*IBS\fR
bytes from \fIIFILE\fR (or less if near the end of the copy) into a copy
buffer. In the absence of the various options and conditions that bypass
the write operation, the copy buffer is then written out to \fIOFILE\fR.
The copy process continues working its way along \fIIFILE\fR and \fIOFILE\fR
until either \fICOUNT\fR is exhausted, an end of file is detected, or an
error occurs. If \fIIBS\fR and \fIOBS\fR are different, ddpt restricts the
value of \fIOBS\fR such that the copy buffer is an integral number of output
blocks (i.e. (((\fIIBS * BPT\fR) % \fIOBS\fR) == 0) ). In the following
descriptions, "segment" refers to all or part of a copy buffer.
.PP
The term "pt device" is used for a pass\-through device to which SCSI
commands like READ(10), WRITE(10) or POPULATE TOKEN may be sent. A pt device
may only be able to process SCSI commands in which case the "pt" flag is
assumed. The ability to recognize such a pt only device may vary depending
on the operating system (e.g. in Linux /dev/sg2 and /dev/bsg/3:0:1:0 are
recognized). However if a device can process either normal UNIX read()/
write() calls or pass\-through SCSI commands then the default is to use
UNIX read()/write() calls. That default can be overridden by using the "pt"
flag (e.g. "if=/dev/sdc iflag=pt"). When pt access is specified any
partition information is
.B ignored.
So "if=/dev/sdc2 iflag=pt skip=3" will start at logical block address 3
of '/dev/sdc'. As a protection measure ddpt will only accept that if the
force flag is also given (i.e. 'iflag=pt,force').
.PP
This utility supports two types of offloaded copies. Both are based on the
EXTENDED COPY (XCOPY or xcopy) family of SCSI commands. The first uses the
XCOPY(LID1) command to do a disk to disk copy. LID1 stands for List
IDentifier length of 1 byte and the command is described in the SPC\-4 drafts
and the earlier SPC\-3 and SPC\-2 standards. Recent SPC\-4 drafts have added
the XCOPY(LID4) sub\-family of copy offloaded commands. There is a subset of
XCOPY(LID4), specialized for offloaded disk to disk copies, that is known by
the market name: ODX. In the descriptions below "xcopy" refers to copies
based on XCOPY(LID1) while "odx" refers to either full or partial ODX copies.
See the XCOPY and ODX sections below for more information.
.SH OPTIONS
The dd\-like options with the name=value syntax are listed first, sorted by
name. Following that, options starting with "\-" are listed.
.TP
\fBbpt\fR=\fIBPT[,OBPC]\fR
where \fIBPT\fR is Blocks Per Transfer. A direct copy is made up of multiple
transfers, each first reading \fIBPT\fR input blocks (i.e. \fIBPT * IBS\fR
bytes) from \fIIFILE\fR into the copy buffer and then from that copy buffer
writing \fI(BPT * IBS) / OBS\fR output blocks to \fIOFILE\fR. This continues
until the copy is finished, with the last transfer being potentially
shorter. The default \fIBPT\fR value varies depending on \fIIBS\fR. When
\fIIBS\fR < 8, \fIBPT\fR is 8192; when \fIIBS\fR < 64, \fIBPT\fR is 1024;
when \fIIBS\fR < 1024, \fIBPT\fR is 128; when \fIIBS\fR < 8192, \fIBPT\fR
is 16; when \fIIBS\fR < 32768, \fIBPT\fR is 4; else \fIBPT\fR defaults
to 1. If \fIBPT\fR is given as 0 it is treated as the default value.
For "bs=512", \fIBPT\fR defaults to 128 so that 64 KiB (or less) is read
from \fIIFILE\fR into the copy buffer. This option is treated differently
in ODX and is typically only needed for testing; see ODX section.
.br
The optional \fIOBPC\fR (Output Blocks Per Check) argument controls
controls the granularity of sparse writes, write sparing and trim checks.
The default granularity is the size of the copy buffer (i.e. \fIBPT * IBS\fR
bytes). That can be reduced by specifying \fIOBPC\fR. The finest
granularity is when \fIOBPC\fR is 1 which implies the unit of each check
is \fIOBS\fR bytes. When \fIOBPC\fR is 0, or not given, the default
granularity is used. Large \fIOBPC\fR values are rounded down so that
\fIOBPC*OBS\fR does not exceed the size of the copy buffer.
.br
odx: may be used to limit the data represented by each ROD. Mainly for
testing.
.TP
\fBbs\fR=\fIBS\fR
where \fIBS\fR is the \fIIFILE\fR and \fIOFILE\fR block size in bytes.
Conflicts with either the "ibs=" or "obs=" options. The value of \fIBS\fR
is placed in \fIIBS\fR and \fIOBS\fR.
If \fIIFILE\fR or \fIOFILE\fR is a "pt" device then \fIBS\fR
.B must
be the logical block size of the device. See the DD DIFFERENCES section
below. The default is 512 bytes; note that newer disks use 4096 byte blocks
with perhaps larger block sizes coming in the future. CD/DVD/BD media use
a logical block size of 2048 bytes.
.TP
\fBcdbsz\fR={6|10|12|16|32}
size of SCSI READ and/or WRITE commands issued to pt devices. The default is
10 byte SCSI command blocks unless calculations indicate that a 4 byte block
number may be exceeded or \fIBPT\fR is greater than 16 bits (i.e. more than
65535 blocks), in which case it defaults to 16 byte SCSI commands.
.TP
\fBcoe\fR={0|1}
set to 1 for continue on error. Applies to errors on input and output for pt
devices but only on input from block devices or regular files. Errors on
other files will stop ddpt. Default is 0 which implies stop on any error. See
the 'coe' flag for more information.
.TP
\fBcoe_limit\fR=\fICL\fR
where \fICL\fR is the maximum number of consecutive bad blocks stepped over
due to "coe=1" on reads before the copy terminates. The default is 0 which is
implies no limit. This option is meant to stop the copy soon after unrecorded
media is detected while still offering "continue on error" capability for
infrequent, randomly distributed errors.
.TP
\fBconv\fR=\fICONVS\fR
see the CONVERSIONS section below.
.TP
\fBcount\fR=\fICOUNT\fR
copy \fICOUNT\fR input blocks from \fIIFILE\fR to \fIOFILE\fR. If this
option is not given (or \fICOUNT\fR is '\-1') then the \fICOUNT\fR may be
deduced from either \fIIFILE\fR or \fIOFILE\fR. See the COUNT section below.
.br
odx: if a gather list is given to \fIskip=SKIP\fR or a scatter list is
given to \fIseek=SEEK\fR then typically \fIcount=COUNT\fR should not be
supplied. This is because a scatter gather list implies a transfer count.
If both are given then ddpt will exit if they are unequal, the force option
can be used to override this action.
.TP
\fBdelay\fR=\fIMS[,W_MS]\fR
after each segment is copied (typically every (\fIIBS\fR * \fIBPT\fR) bytes)
a delay (sleep) of \fIMS\fR milliseconds is performed. The default value for
\fIMS\fR is 0 which implies no delay. If \fIW_MS\fR is given and greater than
0 (its default value) then there is an additional delay of \fIW_MS\fR
milliseconds associated with each actual write operation that is performed.
If \fIMS\fR is greater than 0 then there is not a delay before the first copy
segment (or after the last); if \fIW_MS\fR is greater than 0 then there is
not a delay before the first write segment. These delays can be used for a
bandwidth limiting.
.br
odx: the \fIMS\fR delay is implemented in the same fashion after each ROD is
copied, apart from the last. If \fIW_MS\fR is greater than 0 then that delay
occurs before each WUT command, apart from the first.
.TP
\fBibs\fR=\fIIBS\fR
where \fIIBS\fR is the \fIIFILE\fR block size in bytes. The default value
is \fIBS\fR or its default (512). Conflicts the "bs=" option (i.e. giving
both "bs=512 ibs=512" is considered a syntax error).
.TP
\fBid_usage\fR=\fILIU\fR
xcopy: SCSI EXTENDED COPY parameter list LIST ID USAGE field is set to
\fILIU\fR. The default value is 0 or 2 . \fILIU\fR can be a number between
0 and 3 inclusive or a string. The strings can be either: 'hold' for
0, 'discard' for 2 or 'disable' for 3.
.TP
\fBif\fR=\fIIFILE\fR
read from \fIIFILE\fR. This option must be given (apart from one odx case).
If \fIIFILE\fR is '\-' then stdin is read. Starts reading at the beginning
of \fIIFILE\fR unless \fISKIP\fR is given.
.br
odx: the \fIrtf=RTF\fR option may replace the \fIif=IFILE\fR option as
input. See the ODX section.
.TP
\fBiflag\fR=\fIFLAGS\fR
where \fIFLAGS\fR is a comma separated list of one or more flags outlined
in the FLAGS section below.  These flags are associated with \fIIFILE\fR and
are mostly ignored when \fIIFILE\fR is stdin.
.TP
\fBintio\fR={0|1}
set to 1 for allow signals (SIGINT, SIGPIPE and SIGUSR1 (or SIGINFO)) to be
received during IO from \fIIFILE\fR or IO to \fIOFILE\fR or \fIOFILE2\fR.
Default is 0 which causes these signals to be masked during IO operations
with a check for signals prior each IO. As long as IO operations don't lock
up (e.g. SCSI READ and WRITE commands) the default is the safer option. Even
if IO operations do lock up it is best to let the kernel take care of that.
.TP
\fBiseek\fR=\fISKIP\fR
start reading \fISKIP\fR blocks (each of \fIIBS\fR bytes) from the start of
\fIIFILE\fR. Default is block 0 (i.e. start of file). This option is a
synonym for \fIskip=SKIP\fR, see its description.
.TP
\fBito\fR=\fIITO\fR
odx: \fIITO\fR is the inactivity timeout whose units are seconds. The default
value is 0 which means the copy manager will take the default inactivity
timeout value from the Block Device ROD Token Limits descriptor in the
Third Party Copy VPD page. \fIITO\fR is ignored if it it exceeds the maximum
inactivity timeout value in the same descriptor (unless the force flag is
given).
.TP
\fBlist_id\fR=\fILID\fR
\fILID\fR is the xcopy LIST IDENTIFIER field. It is used to associate an
originating xcopy command with follow\-up commands such as RECEIVE ROD TOKEN
INFORMATION. If given, the \fILID\fR should not clash with any other xcopy
\fILID\fR currently in use on this I_T nexus.
.br
xcopy: \fILID\fR is a 1 byte (8 bit) value whose default value is 1 or,
if id_usage=disable, 0 . \fILID\fR must not exceed 255.
.br
odx: \fILID\fR is a 4 byte (32 bit) value whose default value is 257 (i.e.
0x101) and, if a second default is needed, 258 (0x102) is used. If a
clash is detected on the default list identifier value then the next higher
value is tried (stopping after 10 attempts).
.TP
\fBobs\fR=\fIOBS\fR
where \fIOBS\fR is the \fIOFILE\fR block size in bytes. The default value
is \fIBS\fR or its default (512). Conflicts the "bs=" option (e.g. giving
both "bs=512 obs=512" is considered a syntax error).
If \fIOBS\fR is given then it has the following restriction: the integer
expression (((\fIIBS\fR * \fIBPT\fR) % \fIOBS\fR) == 0) must be true.
Stated another way: the copy buffer size must be an integral multiple of
\fIOBS\fR. If \fIof2=OFILE2\fR is given then \fIOBS\fR is its block size
as well.
.TP
\fBof\fR=\fIOFILE\fR
write to \fIOFILE\fR. The default value is /dev/null . If \fIOFILE\fR is '\-'
then writes to stdout. If \fIOFILE\fR is /dev/null then no actual writes are
performed. If \fIOFILE\fR is '.' (period) then it is treated the same way as
/dev/null . If \fIOFILE\fR exists then it is _not_ truncated
unless "oflag=trunc" is given. See section on DD DIFFERENCES.
.br
odx: if this option (\fIof=OFILE\fR) is not given and the \fIrtf=RTF\fR option
is given then the \fIRTF\fR file may be thought of as receiving the output
in the form of one or more ROD Tokens. See the ODX section.
.TP
\fBof2\fR=\fIOFILE2\fR
write output to \fIOFILE2\fR. The default action is not to do this additional
write (i.e. when this option is not given). \fIOFILE2\fR is assumed to be
a regular file or a fifo (i.e. a named pipe). \fIOFILE2\fR is opened for
writing and is created if necessary. If \fIOFILE2\fR is a fifo (named pipe)
then some other command should be consuming that data (e.g. 'md5sum OFILE2'),
otherwise this utility will block. The write to \fIOFILE2\fR occurs before
the write to \fIOFILE\fR and prior to sparse writing and write sparing
logic. So everything read is written to \fIOFILE2\fR.
.TP
\fBoflag\fR=\fIFLAGS\fR
where \fIFLAGS\fR is a comma separated list of one or more flags outlined
in the FLAGS section. These flags are associated with \fIOFILE\fR and are
ignored when \fIOFILE\fR is /dev/null, '.' (period), or stdout.
.TP
\fBoseek\fR=\fISEEK\fR
start writing \fISEEK\fR blocks (each of \fIOBS\fR bytes) from the start of
\fIOFILE\fR. Default is block 0 (i.e. start of file). This option is a
synonym for \fIseek=SEEK\fR, see its description.
.TP
\fBprio\fR=\fIPRIO\fR
xcopy: SCSI EXTENDED COPY parameter list PRIORITY field is set to \fIPRIO\fR.
The default value is 1 .
.TP
\fBprotect\fR=\fIRDP[,WRP]\fR
where \fIRDP\fR is the RDPROTECT field in SCSI READ commands and \fIWRP\fR
is the WRPROTECT field in SCSI WRITE commands. The default value for both
is 0 which implies no additional protection information will be transferred.
Both \fIRDP\fR and \fIWRP\fR can be from 0 to 7. If \fIRDP\fR is greater
than 0 then \fIIFILE\fR must be a pt device. If \fIWRP\fR is greater than 0
then \fIOFILE\fR must be a pt device. See the PROTECTION INFORMATION section
below.
.TP
\fBretries\fR=\fIRETR\fR
sometimes retries at the host are useful, for example when there is a
transport error. When \fIRETR\fR is greater than zero then SCSI READs and
WRITEs are retried on error, \fIRETR\fR times. Default value is zero.
Only applies to errors on pt devices.
.TP
\fBrtf\fR=\fIRTF\fR
odx: where \fIRTF\fR is a filename. One or more ROD tokens are written to
\fIRTF\fR during a read to tokens variant or a full copy variant. One or
more ROD tokens are read from \fIRTF\fR during a write from token variant.
This option is not required on a full copy variant. ROD Tokens are 512
bytes long and an extra 8 byte (big\-endian) integer containing the 'number
of bytes represented' is placed after each ROD Token if rtf_len is given.
.TP
\fBrtype\fR=\fIRTYPE\fR
odx: where \fIRTYPE\fR is the ROD Type. The default value (0) indicates that
the copy manager (in the source) decides. \fIRTYPE\fR can be a decimal number,
a hex number (prefixed by 0x or with a "h" appended) or one
of "pit\-def", "pit\-vuln", "pit\-pers", "pit\-any" or "zero". The final
truncated word can be spelt out (e.g. "pit\-vulnerable"). The "pit\-" prefix
is a shortening of "point in time" copy. The "zero" causes a special Block
device zero Token to be created.
.TP
\fBseek\fR=\fISEEK\fR
start writing \fISEEK\fR blocks (each of \fIOBS\fR bytes) from the start of
\fIOFILE\fR. Default is block 0 (i.e. start of file). The \fISEEK\fR value
may exceed the number of \fIOBS\fR\-sized blocks in \fIOFILE\fR.
.br
odx: \fISEEK\fR can be a scatter list: comma separated, in the form
seek=A1,N1[,A2,N2...] . The scatter list may alternatively be read from
a file using this form: seek=@<filename> or read from stdin using this form:
seek=\- (or seek=@\-) . A<n> and N<n> are decimal (optionally with a suffix
multiplier) unless a hex indication is given. Hex values are indicated by
either a leading "0x" or a trailing "h". The address (i.e. A<n>) is a 64 bit
unsigned integer while the number of blocks (i.e. N<n>) is a 32 bit integer.
Thus for a block size of 512 bytes, a single scatter gather list element
cannot exceed 4 TB ((2**32 \- 1) * 512). Note that \fICOUNT\fR is a 64 bit
unsigned integer and thus does not have this restriction. There can be
no more than 128 scatter list elements.
.TP
\fBskip\fR=\fISKIP\fR
start reading \fISKIP\fR blocks (each of \fIIBS\fR bytes) from the start of
\fIIFILE\fR. Default is block 0 (i.e. start of file). The \fISKIP\fR value
must be less than the number of \fIIBS\fR\-sized blocks in \fIIFILE\fR.
.br
odx: \fISKIP\fR can be a gather list: comma separated, in the form
skip=A1,N1[,A2,N2...] . The gather list may alternatively be read from
a file using this form: skip=@<filename> or read from stdin using this form:
skip=\- . See the odx section of the \fIseek=SEEK\fR option for further
details.
.TP
\fBstatus\fR=\fISTAT\fR
the \fISTAT\fR value of 'noxfer' suppresses the throughput speed and the
copy time reporting at the end of the copy. A \fISTAT\fR value of 'none'
additionally suppresses the records in and out reporting after the copy.
So 'status=none' makes ddpt act like a traditional Unix command in which "no
news is good news".  The default action of ddpt is to show the throughput (in
megabytes per second) and the time taken to do the copy after the "records
in" and "records out" lines at the end of the copy. As a convenience the
value 'null' is accepted for \fISTAT\fR and does nothing.
.TP
\fBto\fR=\fITO\fR
odx, xcopy: where \fITO\fR is am xcopy originating command timeout in seconds.
The default value is 0 which is converted internally to 600 seconds (10
minutes). Best to set this timeout value well above the expected copy time.
In a odx full copy this timeout is applied to both the POPULATE TOKEN
and WRITE USING TOKEN commands.
.TP
\fBverbose\fR=\fIVERB\fR
as \fIVERB\fR increases so does the amount of debug reporting sent to stderr.
Default value is zero which yields the minimum amount of debug reporting.
A value of 1 reports extra information that is not repetitive. A value
2 reports cdbs and responses for SCSI commands that are not repetitive
(i.e. other that READ and WRITE). Error processing is not considered
repetitive. Values of 3 and 4 yield reporting for all SCSI commands, plus
Unix read() and write() calls, so there can be a lot of output.
If \fIVERB\fR is "\-1" then reporting that would have been sent to stderr
is redirected to /dev/null essentially throwing it away.
.TP
\fB\-h\fR, \fB\-\-help\fR
reports usage message then exits.
.TP
\fB\-o\fR, \fB\-\-odx\fR
indicates to this utility that one of the four odx variants is requested.
See ODX section.
.TP
\fB\-v\fR, \fB\-\-verbose\fR
equivalent of \fIverbose=1\fR. If \fI\-\-verbose\fR appears twice then
that is equivalent to \fIverbose=2\fR. Also \fI\-vv\fR is equivalent to
\fIverbose=2\fR.
.TP
\fB\-V\fR, \fB\-\-version\fR
reports version number information then exits.
.TP
\fB\-w\fR, \fB\-\-wscan\fR
this option is available in Windows only. It lists storage device names
and the corresponding volumes, if any. When used twice it adds the "bus
type" of the closest transport (e.g. a SATA disk in a USB connected
enclosure has bus type USB). When used three times a SCSI adapter scan
is added. When used four times only a SCSI adapter scan is shown.
See EXAMPLES section below and the README.win32 file.
.TP
\fB\-x\fR, \fB\-\-xcopy\fR
this option will attempt to call the SCSI EXTENDED COPY(LID1) command. In
the absence of another indication the xcopy command will be sent to the
destination (i.e. \fIOFILE\fR). See the section on ENVIRONMENT VARIABLES
below.
.SH COUNT
When the \fIcount=COUNT\fR option is not given (or \fICOUNT\fR is '\-1')
then an attempt is made to deduce \fICOUNT\fR as follows.
.PP
When both or either \fIIFILE\fR and \fIOFILE\fR are block devices, then
the minimum size, expressed in units of input blocks, is used. When both
or either \fIIFILE\fR and \fIOFILE\fR are pass\-through devices, then the
minimum size, expressed in units of input blocks, is used.
.PP
If a regular file is used as input, its size, expressed in units of input
blocks (and rounded up if necessary) is used. Note that the rounding up
of the deduced \fICOUNT\fR may result in a partial read of the last input
block and a corresponding partial write to \fIOFILE\fR if it is a regular
file. After a regular file to regular file copy the length of \fIOFILE\fR
will be the same as \fIIFILE\fR unless \fIOFILE\fR existed and its length
was already greater than that of \fIIFILE\fR. To get a copy like the
standard Unix cp command, use oflag=trunc with ddpt.
.PP
The size of pt devices is deduced from the SCSI READ CAPACITY command.
Block device sizes (or their partition sizes) are obtained from the
operating system, if available.
.PP
If \fIskip=SKIP\fR or \fIskip=SEEK\fR are given and the \fICOUNT\fR is
deduced (i.e. not explicitly given) then that size is scaled back so
that the copy will not overrun the file or device.
.PP
If \fICOUNT\fR is not given and \fIIFILE\fR is a fifo (and stdin is
treated as a fifo) then \fIIFILE\fR is read until an EOF is detected.
If \fICOUNT\fR is not given and \fIIFILE\fR is a /dev/zero (or
equivalent) then zeros are read until an error occurs (e.g. file
system full).
.PP
If \fICOUNT\fR is not given and cannot be deduced then an error message
is issued and no copy takes place.
.SH CONVERSIONS
One or more conversions can be given to the "conv=" option. If more than
one is given, they should be comma separated. ddpt does not perform the
traditional dd conversions (e.g. ASCII to EBCDIC). Recently added
conversions inherited from GNU's dd overlap somewhat with the some of ddpt
flags.
.TP
fdatasync
equivalent to "oflag=fdatasync". Flushes data associated with the
\fIOFILE\fR to storage at the end of the copy. This conversion is
for compatibility with GNU's dd.
.TP
fsync
equivalent to "oflag=fsync". Flushes data and meta\-data associated
with the \fIOFILE\fR to storage at the end of the copy. This conversion
.TP
no_del_tkn
equivalent to "oflag=no_del_tkn".
.TP
noerror
this conversion is very close to "iflag=coe" and is treated as such. See
the "coe" flag. Note that an error on a block device or regular file
\fIOFILE\fR will stop the copy.
.TP
notrunc
this conversion is accepted for compatibility with dd and ignored since
the default action of this utility is not to truncate \fIOFILE\fR.
.TP
null
has no affect, just a placeholder.
.TP
resume
See "resume" in the FLAGS sections for more information.
.TP
rtf_len
equivalent to "oflag=rtf_len".
.TP
sparing
See "sparing" in the FLAGS sections for more information.
.TP
sparse
FreeBSD's dd supports "conv=sparse" and now GNU's dd does as well so the
same syntax is supported in ddpt. See "sparse" in the FLAGS sections for
more information.
.TP
sync
is ignored by ddpt. With dd it means supply zero fill (rather than skip)
and is typically used like this "conv=noerror,sync" to have the same
functionality as ddpt's "iflag=coe".
.TP
trunc
if \fIOFILE\fR is a regular file then truncate it prior to starting the
copy. See "trunc" in the FLAGS section.
.SH FLAGS
A list of flags and their meanings follow. The flag name is followed
by one or two indications in square brackets. The first indication is
either "[i]", "[o]" or "[io]" indicating this flag is active for the
\fIIFILE\fR, \fIOFILE\fR or both the \fIIFILE\fR and the \fIOFILE\fR. The
second indication contains some combination of "reg", "blk" "pt", "odx",
or "xcopy". These indicate whether the flag applies to a regular file, a
block device (accessed via Unix read() and write() commands, a pass\-through
device, an ODX offloaded copy or a XCOPY(LID1) offloaded copy respectively.
Other special file types that are sometimes referred to are "fifo"
and "tape".
.TP
append [o] [reg], [io] [odx]
causes the O_APPEND flag to be added to the open of \fIOFILE\fR. For regular
files this will lead to data being appended to the end of any existing
data. Conflicts the \fIseek=SEEK\fR option. The default action of this
utility is to overwrite any existing data from the beginning of \fIOFILE\fR
or, if \fISEEK\fR is given, starting at block \fISEEK\fR. Note that
attempting to 'append' to a device file (e.g. a disk) will usually be
ignored or may cause an error to be reported.
.br
odx: if the \fIrtf=RTF\fR option is given, \fIRTF\fR exists, is a regular
file and this utility wants to write to \fIRTF\fR then new ROD Tokens are
appended to \fIRTF\fR. The default action is to truncate \fIRTF\fR before
new ROD Tokens are written to it.
.TP
block [io] [pt]
pass\-through file opens are non\-blocking by default and may report the
pt device is busy. Use this flag to open blocking so utility may wait until
another process locking (or with an exclusive open) is complete before
continuing.
.TP
cat [io] [xcopy]
xcopy: set CAT (residual data handling) bit in EXTENDED COPY(LID1) parameter
list segment descriptor header. May appear in either flag list when xcopy is
being used. Works with the PAD bit for handling residual data on the
destination side. See the XCOPY section below.
.TP
coe [io] [pt], [i] [reg,blk]
continue on error. 'iflag=coe oflag=coe' and 'coe=1' are equivalent.
Errors occurring on output regular or block files will stop ddpt.
Error messages are sent to stderr. This flag is similar
to 'conv=noerror,sync' in the
.B dd(1)
utility. Unrecovered errors are counted and reported in the summary at
the end of the copy.
.IP
This paragraph concerns coe on pt devices. A medium, hardware or blank
check error during a read operation will will cause the following: first
re\-read blocks prior to the bad block, then try to recover the bad
block (supplying zeros if that fails), and finally re\-read the blocks
after the bad block. A medium, hardware or blank check error while writing
is reported but otherwise ignored. SCSI disks may automatically try and
remap faulty sectors (see the AWRE and ARRE in the read write error
recovery mode page (the sdparm utility can access these attributes)). If
bad LBAs are reported by the pass\-through then the LBA of the lowest and
highest bad block is also reported.
.IP
This paragraph concerns coe on input regular files and block devices.
When a EIO or EREMOTEIO error is detected on a normal segment read then
the segment is re\-read one block (i.e. \fIIBS\fR bytes) at a time. Any
block that yields a EIO or EREMOTEIO error is replaced by zeros. Any
other error, a short read or an end of file will terminate the copy,
usually after the data that has been read is written to the output file.
.TP
dc [io] [blk,pt]
xcopy: set DC (destination counter) bit in EXTENDED COPY(LID1) parameter
list segment descriptor header. May appear in either flag list when xcopy is
being used.
.TP
direct [io] [reg,blk]
causes the O_DIRECT flag to be added to the open of \fIIFILE\fR and/or
\fIOFILE\fR. This flag requires some memory alignment on IO. Hence user
memory buffers are aligned to the page size. May have no effect on pt
devices. This flag will bypass caching/buffering normally done by block
layer. Beware of data coherency issues if the same locations have been
recently accessed via the block layer in its normal mode (i.e.
non\-direct). See open(2) man page.
.TP
dpo [io] [pt]
set the DPO bit (disable page out) in SCSI READ and WRITE commands. Not
supported for 6 byte cdb variants of READ and WRITE. Indicates that
data is unlikely to be required to stay in device (e.g. disk) cache.
May speed media copy and/or cause a media copy to have less impact
on other device users.
.TP
errblk [i] [pt] [experimental]
attempts to create or append to a file called "errblk.txt" in the current
directory the logical block addresses of blocks that cannot be read. The
first (appended) line is "# start <timestamp>". That is followed by the
LBAs in hex (and prefixed with "0x") of any block that cannot be read,
one LBA per line. If the sense data does not correctly identify the LBA of
the first error in the range it was asked to read then a LBA range is
reported in the form of the lowest and the highest LBA in the range
separated by a "\-". At the end of the copy a line with "# stop <timestamp>"
is appended to "errblk.txt". Typically used with "coe".
.TP
excl [io] [reg,blk]
causes the O_EXCL flag to be added to the open of \fIIFILE\fR and/or
\fIOFILE\fR. See open(2) man page.
.TP
fdatasync [o] [reg,blk]
Flushes data associated with the \fIOFILE\fR to storage at the end of the
copy.
.TP
flock [io] [reg,blk,pt]
after opening the associated file (i.e. \fIIFILE\fR and/or \fIOFILE\fR)
an attempt is made to get an advisory exclusive lock with the flock()
system call. The flock arguments are "FLOCK_EX | FLOCK_NB" which will
cause the lock to be taken if available else a "temporarily unavailable"
error is generated. An exit status of 90 is produced in the latter case
and no copy is done. See flock(2) man page.
.TP
force [io] [pt] [xcopy,odx]
override difference between given block size and the block size found
by the SCSI READ CAPACITY command. Use the given block size. Without
this flag the copy would not be performed. pt access to what appears
to be a block partition is aborted in version 0.92; that can be overridden
by the force flag. For related reasons the 'norcap' flag requires this
flag when applied to a block device accessed via pt.
.br
xcopy and odx: various limits imposed by associated VPD pages or the RECEIVE
COPY OPERATING PARAMETERS command can be overridden (i.e.  exceeded) if this
flag is given. Note that the copy manager will probably object.
.TP
fsync [o] [reg,blk]
Flushes data and metadata (describing the file) associated with the
\fIOFILE\fR to storage at the end of the copy.
.TP
fua [io] [pt]
causes the FUA (force unit access) bit to be set in SCSI READ and/or WRITE
commands. The 6 byte variants of the SCSI READ and WRITE commands do not
support the FUA bit.
.TP
fua_nv [io] [pt]
causes the FUA_NV (force unit access non\-volatile cache) bit to be set in
SCSI READ and/or WRITE commands. This only has an effect with pt devices.
The 6 byte variants of the SCSI READ and WRITE commands do not support the
FUA_NV bit. The FUA_NV bit was made obsolete in SBC\-3 revision 35d.
.TP
ignoreew [o] [tape]
ignore the early warning indication (of end of tape) when writing to tape.
See TAPE section.
.TP
immed [io] [odx]
sets the IMMED bit in the POPULATE TOKEN (when [i]) or WRITE USING
TOKEN (when [o]) command. That command should return status promptly after
starting the data transfer. The RECEIVE ROD TOKEN INFORMATION command is then
used to poll for completion. SCSI command timeouts should not be exceeded,
even for very large RODs, if this flag is used.
.TP
nocache [io] [reg,blk]
use posix_fadvise(POSIX_FADV_DONTNEED) to advise corresponding file there is
no need to fill the file buffer with recently read or written blocks. If
used with "iflag=" it will increase the read ahead on \fIIFILE\fR.
.TP
no_del_tkn [o] [odx]
will clear the DEL_TKN bit on the last WRITE USING TOKEN command of each ROD
Token in a odx full copy. In a large odx full copy several ROD Tokens may
be used (one after the other). The default action is to set the DEL_TKN bit
on the last WUT command of each ROD. Either way it should not make much
difference because the copy manager deletes a ROD Token after a copy is
completed. The copy manager will also delete/invalidate a ROD Token if the
inactivity timeout is reached.
.TP
nofm [o] [tape]
no File Mark (FM) on close when writing to tape. See TAPE section.
.TP
nopad [o] [tape]
when the block to be written to a tape drive contains less than \fIOBS\fR
bytes, then this option causes the partial block to be written as is. The
default action for a tape in this case is to pad the block. See TAPE section.
.TP
norcap [io] [pt]
do not perform SCSI READ CAPACITY command on the corresponding pt device.
If used on block device accessed via pt then 'force' flag is also
required. This is to warn about using pt access on what may be a block
device partition.
.TP
nowrite [o] [reg,blk,pt]
bypass writes to \fIOFILE\fR. The "records out" count is not incremented.
\fIOFILE\fR is still opened but "oflag=trunc" if given is ignored. Also
the ftruncate call associated with the sparse flag is ignored (i.e.
bypassed). Commands such as trim and SCSI SYNCHRONIZE CACHE are still sent.
.TP
null [io]
has no affect, just a placeholder.
.TP
odx [io] [odx]
indicates to this utility that one of the four variants of an odx copy is
requested. Using any of the \fI\-\-odx\fR, \fIrtf=RTF\fR or \fIrtype=RTYPE\fR
options also indicates that odx is requested. See the ODX section.
.TP
pad [o] [reg,blk,pt], [io] [xcopy]
when the block to be written (typically the last block) contains less than
\fIOBS\fR bytes, then this option causes the block to be padded with
zeros (i.e. bytes of binary zero). The default action for a regular file
and a fifo is to do a partial write. The default action of a block
and a pt device is to ignore the partial write. The default action of
a tape is to pad, so this flag is not needed (see the nopad flag).
.br
xcopy: sets the PAD bit in the CSCD descriptor of the associated \fIIFILE\fR
or \fIOFILE\fR. Is associated with residual data handling and works
together with the cat flag. See the XCOPY section below.
.TP
prealloc [o] [reg]
use the fallocate() call prior to starting a copy to set \fIOFILE\fR to its
expected size.
.TP
pt [io] [blk,pt]
causes a device to be accessed in "pt" mode. In "pt" mode SCSI READ and
WRITE commands are sent to access blocks rather than standard UNIX read()
and write() commands. The "pt" mode may be implicit if the device is only
capable of passing through SCSI commands (e.g. the /dev/sg* and
some /dev/bsg/* devices in Linux). This flag is needed for device nodes
that can be accessed both via standard UNIX read() and write() commands
as well as SCSI commands. Such devices default standard UNIX read()
and write() commands in the absence of this flag.
.TP
rarc [i] [pt]
bit set in READ(10, 12, 16 and 32) to suppress RAID rebuild functions
when a bad (or recovered after difficulties) block is detected.
.TP
resume [o] [reg]
when a copy is interrupted (e.g. with Control\-C from the keyboard)
then using the same invocation again with the addition of "oflag=resume"
will attempt to restart the copy from the point of the interrupt (or
just before that point). It is harmless to use "oflag=resume" when
\fIOFILE\fR doesn't exist or is zero length. If the length of \fIOFILE\fR
is greater than or equal to the length implied by a ddpt invocation that
includes "oflag=resume" then no further data is copied.
.TP
self [io] [pt]
used together with trim flag to do a self trim (trim of segments of a
pt device that contain all zeros). If \fIOFILE\fR is not given, then
it is set to the same as \fIIFILE\fR. If \fISEEK\fR is not given it
set to the same value as \fISKIP\fR (possibly adjusted if \fIIBS\fR
and \fIOBS\fR are different). Implicitly sets "nowrite" flag.
.TP
sparing [o] [reg,blk,pt]
during the copy each \fIIBS\fR * \fIBPT\fR byte segment is read from
\fIIFILE\fR into a buffer. Then, instead of writing that buffer to
\fIOFILE\fR, the corresponding segment is read from \fIOFILE\fR into another
buffer. If the two buffers are different, the former buffer is written to
the \fIOFILE\fR. If the two buffers compare equal then the write to
\fIOFILE\fR is not performed. Write sparing is useful when a write operation
is significantly slower than a read. Under some conditions flash memory
devices have slow writes plus an upper limit on the number of times the same
cell can be rewritten. The granularity of the comparison can be reduced from
the default \fIIBS\fR * \fIBPT\fR byte segment with the the \fIOBPC\fR value
given to the "bpt=" option. The finest granularity is when \fIOBPC\fR is 1
which implies \fIOBS\fR bytes.
.TP
sparse [o] [reg,blk,pt]
after each \fIIBS\fR * \fIBPT\fR byte segment is read from \fIIFILE\fR, it
is checked to see if it is all zeros. If so, that segment is not written to
\fIOFILE\fR. See the section on SPARSE WRITES below. The granularity of
the zero comparison can be reduced from the default \fIIBS\fR * \fIBPT\fR
byte segment with the \fIOBPC\fR value given to the "bpt=" option.
.TP
ssync [o] [pt]
if \fIOFILE\fR is in "pt" mode then the SCSI SYNCHRONIZE CACHE command is
sent to \fIOFILE\fR at the end of the copy.
.TP
strunc [o] [reg]
perform a sparse copy with a ftruncate system call to extend the length
of the \fIOFILE\fR if required. See the sparse flag and the section on
SPARSE WRITES below.
.TP
sync [io] [reg,blk]
causes the O_SYNC flag to be added to the open of \fIIFILE\fR and/or
\fIOFILE\fR. See open(2) man page.
.TP
rtf_len [io] [odx]
odx: with the 'read to tokens' variant, after 512 bytes of each ROD Token
are written to \fIIRTF\fR an additional 8 byte (big endian) integer is
written. That integer is the number of bytes the associated ROD represents.
The draft standards say for standard ROD types the ROD Token holds this
value. However vendor specific ROD types may be used or the vendors may
choose not to comply. Either way the 'write from tokens' variant needs to
know the size of the ROD it is writing from.
.TP
trim [io] [pt] [experimental]
similar logic to the "sparse" option. However instead of skipping segments
that are full of zeros a "trim" command is sent to \fIOFILE\fR. Usually set
as an oflag argument but for self trim can be used as an iflag
argument (e.g. "iflag=self,trim"). Depending on the usage this may require
the device to support "deterministic read zero after trim". See the
TRIM, UNMAP AND WRITE SAME section below.
.TP
trunc [o] [reg]
if \fIOFILE\fR is a regular file then it is truncated prior to starting the
copy. If \fISEEK\fR is not given or 0 then \fIOFILE\fR is truncated to zero
length; when \fISEEK\fR is larger than zero the truncation takes place at
file byte pointer \fISEEK*OBS\fR.  Ignored if "oflag=append". Conflicts
with "oflag=sparing".
.TP
unmap [io] [pt]
same as the trim flag.
.TP
xcopy [io] [pt]
invoke SCSI XCOPY(LID1) logic and send the XCOPY command to the either
\fIIFILE\fR or \fIOFILE\fR depending on which flag this called. If both are
given (i.e. an invocation including 'iflag=xcopy  oflag=xcopy') then send
the XCOPY(LID1) to \fIOFILE\fR.
.SH XCOPY
This section describes XCOPY(LID1) support with this utility. For ODX
support (XCOPY(LID4) subset) see the ODX section.
.PP
A device (logical unit (LU)) that supports XCOPY operations should set
the 3PC field (3PC stands for Third Party Copy) in its standard INQUIRY
response. That is not checked when this utility does an xcopy operation
but if it fails, that is one thing that the user may want to check.
.PP
If the xcopy starts and fails while underway, then 'sg_copy_results \-s'
may be useful to view the copy status. It might also be used from a
different process with the same I_T nexus (i.e. the same machine)
to check status during an xcopy operation.
.PP
The \fIpad\fR and \fIcat\fR flags control the handling of residual
data. As the data can be specified either in terms of source or target
block size and both might have different block sizes residual data is
likely to happen in these cases.
If both block sizes are identical these bits have no effect as
residual data will not occur.
.PP
If neither of these flags are set, the EXTENDED COPY command will be
aborted with additional sense 'UNEXPECTED INEXACT SEGMENT'.
.PP
If only the \fIcat\fR flag is set the residual data will be retained
and made available for subsequent segment descriptors. Residual data
will be discarded for the last segment descriptor.
.PP
If the \fIpad\fR flag is set for the source descriptor only, any
residual data for both source or destination will be discarded.
.PP
If the \fIpad\fR flag is set for the target descriptor only any
residual source data will be handled as if the \fIcat\fR flag is set,
but any residual destination data will be padded to make a whole block
transfer.
.PP
If the \fIpad\fR flag is set for both source and target any residual
source data will be discarded, and any residual destination data will
be padded.
.PP
There is a web page discussing ddpt, XCOPY and ODX at
http://sg.danny.cz/sg/ddpt_xcopy_odx.html
.SH ODX
This section describes ODX support (an XCOPY(LID4) subset) for this utility.
ODX descriptions use the following command name abbreviations: PT for
the POPULATE TOKEN command, RRTI for the READ ROD TOKEN INFORMATION command,
and WUT for the WRITE USING TOKEN command.
.PP
A device (logical unit (LU)) that supports ODX operations is required to set
the 3PC field (3PC stands for Third Party Copy) in its standard INQUIRY
response and support the Third Party Copy VPD page. If this utility generates
errors noting the absence of these then the device in question probably does
not support ODX.
.PP
There a four variants of ODX supported by ddpt:
.br
  \fBfull copy\fR : ddpt \-\-odx if=/dev/sg3 bs=512 of=/dev/sg4
.br
  \fBzero output blocks\fR : ddpt if=/dev/null rtype=zero bs=512 of=/dev/sg4
.br
  \fBread to tokens\fR : ddpt if=/dev/sg3 bs=512 skip=@gath.lst rtf=a.rt
.br
  \fBwrite from tokens\fR : ddpt rtf=a.rt bs=512 of=/dev/sg4 seek=@scat.lst
.PP
The full copy will call PT and WUT commands repeatedly until the copy is
complete. More precisely the full copy will make the largest single call
to PT allowed by the input's Third Party Copy VPD page (and, if given,
allowed by the \fIBPT\fR argument in the \fIbpt=BPT[,OBPC]\fR option). Then
one or more WUT calls are made to write out from the ROD created by the PT
step. The largest single WUT call is constrained by the output's Third Party
Copy VPD page (and, if given, allowed by the \fIOBPC\fR argument in the
\fIbpt=BPT[,OBPC]\fR option). This sequence continues until the requested
copy is complete.
.PP
The zero output blocks variant is a special case of the full copy in
which only WUT calls are made. ODX defines a special ROD Token to
zero blocks. That special ROD Token has a fixed pattern (shown in SBC\-3)
and does not need to be created by a PT command like normal ROD Tokens.
.PP
The read to tokens and the write from tokens variants are designed to be
the read (input) and write (output) sides respectively of a network copy.
Each can run on different machines by sending the \fIRTF\fR file from
the machine doing the read to the machine doing the write. The read to
tokens will make one or more PT calls and output the resulting ROD Tokens
to the \fIRTF\fR file. \fIRTF\fR might be a regular file or a named pipe.
.PP
All four variants can have the immed flag set. Then the PT and/or WUT
commands are issued with the IMMED bit set and the RRTI command is used to
poll for completion. The delay between the polls is as suggested by the
RRTI command (or if no suggestion is made, 500 milliseconds). Either
iflag=immed, oflag=immed or both can be given but are only effective if
the corresponding \fIIFILE\fR or \fIOFILE\fR sends a PT or WUT command.
.PP
Typically there is no need to give the \fIlist_id=LID\fR option. If this
option is not given then 257 is chosen. If that is busy then 258 is tried.
That continues until a usable \fILID\fR is found or 10 \fILID\fRs have been
tried. In the latter case ddpt exits with status of 55 (operation in
progress). If the user gives \fIlist_id=LID\fR option and \fILID\fR is
busy then ddpt exits with exit status 55.
.PP
If the block size of the input and output are different (i.e. \fIIBS\fR
is not equal to \fIOBS\fR) then one must be a multiple of the other. So
an input block size of 512 bytes and an output block size of 4096
bytes (or vice versa) is acceptable.
.PP
The four ODX variants are distinguished as follows: if \fIOFILE\fR is a
pass\-through device, if=/dev/null (or equivalent) and rtype=zero then the
zero output blocks variant is selected. If both \fIIFILE\fR and \fIOFILE\fR
are pass\-through devices and there is some indication of an ODX request (e.g.
the \fI\-\-odx\fR option), then the full copy variant is selected. The read
to tokens and the write from token variants are indicated by the absence
of either a \fIof=OFILE\fR or a \fIif=IFILE\fR option, respectively, plus
the presence of a \fIrtf=RTF\fR option.
.PP
The helper utility ddptctl contains options to issue a single PT, RRTI,
WUT or COPY OPERATION ABORT command. It can also issue a series of
polling RRTI commands. It can decode information in ROD Tokens (which is
not as informative as it should be) and print the number of blocks and block
size of a disk, plus protection information if available. See ddptctl.
.PP
There is a web page discussing ddpt, XCOPY and ODX at
http://sg.danny.cz/sg/ddpt_xcopy_odx.html
.SH SPARSE WRITES
Bypassing writes of blocks full of zeros can save a lot of IO. However
with regular files, bypassed writes at the end of the copy can lead
to an \fIOFILE\fR which is shorter than it would have been without
sparse writes. This can lead to integrity checking programs like md5sum
and sha1sum generating different values.
.PP
This utility has two ways of handling this file length problem: writing
the last block (even if it is full of zeros) or using the ftruncate
system call. A third approach is to ignore the problem (i.e. leaving
\fIOFILE\fR shorter). The ftruncate approach is used when "oflag=strunc"
while the last block is written when "oflag=sparse". To ignore the
file length issue use "oflag=sparse,sparse". Note that if \fIOFILE\fR's
length is already correct or longer than required, no action is taken.
.PP
The support for sparse writing of regular files may depend on the OS, the
file system and the settings of \fIOFILE\fR. POSIX makes few guarantees
when the ftruncate system call is used to extend a file's length, as may
occur when "oflag=strunc". Further, primitive file systems like VFAT may not
accept sparse writes or simulate the effect by writing blocks of zeros. The
latter approach will defeat any sparse writing performance gain.
.SH TRIM, UNMAP AND WRITE SAME
This is a new storage feature often associated with Solid State
Disks (SSDs) or disk arrays with "thin provisioning". In the ATA command
set (ACS\-2) the relevant command is DATA SET MANAGEMENT with the TRIM
bit set. In the SCSI command set (SBC\-3) it is either the UNMAP or
WRITE SAME command. Note there is no TRIM command however the term is
frequently used in the technical press.
.PP
Trim is a way of telling a storage device that blocks are no longer needed.
Keeping the pool of unwritten blocks large is important for the write
performance of SSDs and the thrifty use of real storage in thin provisioned
arrays. Currently file systems in recent OSes may issue trims associated
with file deletes. The trim option in ddpt may be useful when a partition
or a whole SSD is to be "deleted". Note that ddpt is bypassing file
systems in that it only offers trim on pass\-through (pt) devices.
.PP
This utility issues SCSI commands to pt devices and for "trim" currently
issues a SCSI WRITE SAME(16) command with the UNMAP bit set. If the pt
device is a SSD with a ATA interface then recent versions of Linux
will translate the SCSI WRITE SAME to the ATA DATA SET MANAGEMENT command
with the TRIM bit set. The maximum size of each "trim" command sent
is the size of the copy buffer (i.e. \fIIBS\fR * \fIBPT\fR bytes). And
that maximum can be reduced with the \fIOBPC\fR argument of the "bpt="
option.
.PP
The trim can be used various ways. One way is a copy where the copy
buffer (or some part of it) is checked for zeros as is done by the
sparse oflag. When a zero segment is found, a trim "command" is
sent to the \fIOFILE\fR. For example:
.PP
   ddpt if=dsk.img bs=512 of=/dev/sdc oflag=pt,trim
.PP
The copy buffer is 64 KiB (since \fIBPT\fR and \fIOBPC\fR default to 128
when "bs=512") and it is checked for all zeros. If it is all zeros then
a trim command is sent to the corresponding location of /dev/sdc
which is accessed via the pt interface. If it is not all zeros
then a SCSI WRITE command is sent. Another way is to trim all or
part of a disk. To trim a whole disk (i.e. deleting all its data):
.PP
   ddpt if=/dev/zero bs=512 of=/dev/sdc oflag=pt,trim
.PP
A third way is to "self\-trim" which is to only trim those parts
of a disk that contain segments full of zeros:
.PP
   ddpt if=/dev/sdc skip=0x2300 bs=512 iflag=pt,self,trim count=0x1234f0
.PP
The "self" oflag automatically sets up the output side of the copy
to send trim commands (if required) back the the same device (i.e. /dev/sdc).
If this example was self\-trimming a partition then the partition would
start at LBA 0x2300 and be 0x1234f0 blocks long.
.PP
Some random product examples: the Intel X25\-M G2 SSDs have trim with
recent firmware and they do deterministic read zero after trim. The
Seagate Pulsar SSD has an ATA interface which supports the deterministic
reads of zero after the DATA SET MANAGEMENT command with the TRIM option.
.SH DD DIFFERENCES
dd defaults "if=" and "of=" to stdin and stdout respectively. This follows
Unix filter conventions. However since dd and ddpt are often used to read
binary data for timing purposes, having to supply "of=/dev/null" can
be easily forgotten. Without it dd will typically spew binary data on the
console. So ddpt has changed its defaults: the "if=\fIIFILE\fR" is now
mandatory for direct copies and to read from stdin "if=\-" can be
used; "of=\fIOFILE\fR" remains optional but its default changes
to "/dev/null" (or "NUL" in Windows). To send output to stdout ddpt
accepts "of=\-".
.PP
dd truncates \fIOFILE\fR unless "conv=notrunc" is given. When dd truncates,
it truncates to zero length unless \fISEEK\fR is greater than zero. ddpt
does not truncate \fIOFILE\fR by default. If \fIOFILE\fR exists it will be
overwritten. The overwrite starts at block zero unless \fISEEK\fR
or "oflag=append" is given. If \fIOFILE\fR is a regular file
then "oflag=trunc" (or "conv=trunc") will truncate \fIOFILE\fR prior to the
copy.
.PP
Numeric arguments to ddpt can be given in hexadecimal, either with a
leading "0x" or "0X" or with a trailing "h". Note that dd accepts "0x123"
but interprets it as "0 * 123" (i.e. zero). ddpt will also interpret "x"
as multiplies unless the left operand is zero (e.g. "0x123"). So both
dd and ddpt will interpret "skip=2x123" as "skip=246".
.PP
Terabyte size disks make it impractical to copy all the data into a buffer
before writing it out. Therefore both dd and ddpt read a relatively small
amount of data into a copy (or transfer) buffer then write it out to the
destination, repeating this process until the \fICOUNT\fR is exhausted.
.PP
A major difference in ddpt is the addition of \fIBPT\fR to control the
size of the copy buffer. With dd, \fIIBS\fR is the size of the copy buffer
and the unit of \fISKIP\fR and \fICOUNT\fR. With ddpt, \fIIBS\fR * \fIBPT\fR
is the size of the copy buffer and \fIIBS\fR is the unit of \fISKIP\fR
and \fICOUNT\fR. This allows ddpt to have its \fIIBS\fR set to the logical
block size of \fIIFILE\fR without unduly restricting the size of the copy
buffer. And setting \fIIBS\fR (and \fIOBS\fR for \fIOFILE\fR) accurately
is required when the pass\-through interface is used since with the SCSI
READ and WRITE commands the logical block size is implicit.
.PP
The way dd handles its copy buffer (outlined in SUSv4 description of dd)
is relatively complex, especially when \fIIBS\fR and \fIOBS\fR are different
sizes. The restriction that ddpt places on \fIIBS\fR and \fIOBS\fR (
i.e. (((\fIIBS * BPT\fR) % \fIOBS\fR) == 0) ) means that a single
copy buffer can be used since its size is a multiple of both \fIIBS\fR and
\fIOBS\fR. Being able to precisely define the copy buffer size in ddpt
makes sparse writing, write sparing and trim operations simpler to
define and the user to control.
.PP
ddpt does not support dd's "cbs=" option (conversion block size). If
the "cbs=" option is given to ddpt then it is ignored.
.PP
ddpt adds two types of disk to disk, offloaded copies: XCOPY(LID1) first
introduced in SPC\-2 (standardized in 2001), and ODX which is a subset of
XCOPY(LID4) first introduced in SPC\-4 draft (revision 34, 2012).
.SH PROTECTION INFORMATION
This section is about protection information which is typically an extra 8
bytes associated with each logical block. Those 8 byte are divided into 3
fields: logical block guard (16 bit (2 byte) CRC), logical block application
tag (2 bytes) and the logical block reference tag (4 bytes). The acronym
DIF is sometimes used for protection information.
.PP
The feature to read and/or write protection information by using the
\fIprotect=RDP[,WRP]\fR option is currently experimental. It should be used
with care and may not "play well" with some other features such as write
sparing and sparse writing. It should be used to copy user data plus the
associated protection information to or from a regular file. It could also
be used for a device to device copy assuming the "pt" interface is used
for both. Also only modern SCSI disks support protection information.
.PP
When \fIRDP\fR or \fIWRP\fR is greater than 0 then a copy with associated
protection information is active. In this state \fIIBS\fR and \fIOBS\fR
must be the same and equal to the logical block size of the device(s)
formatted with protection information. If a SCSI disk with 512 byte logical
block size has protection information then the actual number of bytes
transferred for each logical block is typically 520 bytes. For such a disk
\fIBS=512\fR is required even when additional protection information is
being transferred.
.SH MULTIPLIERS
By default numeric arguments to options are assumed to be decimal. Almost
all numeric arguments to options (e.g. \fICOUNT\fR in the \fIcount=COUNT\fR
option) may include one of these multiplicative suffixes:
c C *1; w W *2; b B *512; k K KiB *1,024; KB *1,000; m M MiB *1,048,576;
MB *1,000,000 . This pattern continues for "G", "T" and "P". The latter two
suffixes can only be used for 64 bit values. Some numeric arguments are
limited to 32 bit values (e.g. \fIBS\fRin the \fIbs=BS\fR option).
Also a suffix of the form "x<n>" multiplies the leading number by <n>;
however the combinations "0x" and "0X" are treated differently, see the
next paragraph. These multiplicative suffixes are compatible with GNU's
dd command (since 2002) which claims compliance with the SI and with
IEC 60027\-2 standards.
.PP
Alternatively numerical values can be given in hexadecimal indicated by
either a leading "0x" or "0X", or by a trailing "h" or "H". When hex numbers
are given, suffix multipliers cannot be used.
.PP
If a numeric argument is required to fit in 32 bits and is too large then
an error is reported. Usually negative numbers are not permitted
but "count=-1" is a special case and means "all available"; "verbose=-1"
is another special case.
.SH NOTES
A partial write is a write to the \fIOFILE\fR of less than \fIOBS\fR
bytes. This typically occurs at the end of a copy. dd can do partial
writes. ddpt does partial writes to regular files and fifos (including
stdout). However ddpt ignores partial writes when \fIOFILE\fR is a block
device or a pt device. When ddpt ignores a partial write, it sends a
warning to the console (stderr).
.PP
At the end of the copy two lines are reported to the console:
.br
   <in_full>+<in_partial> records in
.br
   <out_full>+<out_partial> records out
.PP
The "records in" line is the number of full input blocks (each of
\fIIBS\fR bytes) that have been read plus the number of partial blocks (
usually less than \fIIBS\fR bytes) that have been read. Following the lead
of dd when 'iflag=coe' is active a block that cannot be read (and has zeros
substituted for its output) is regarded as a partial read. The "records out"
line is the number of full output blocks (each of \fIOBS\fR bytes) that
have been written plus the number of partial blocks (usually less than
\fIOBS\fR bytes) that have been written.
.PP
Block devices (e.g. /dev/sda and /dev/hda) can be given for \fIIFILE\fR.
If neither 'iflag=direct' nor 'iflag=pt' is given then normal block IO
involving buffering and caching is performed. If 'iflag=direct' is given
then the buffering and caching is bypassed (this is applicable to both SCSI
devices and ATA disks). When 'iflag=pt' is given SCSI commands are sent to
the device which bypasses most of the actions performed by the block layer.
The same applies for block devices given for \fIOFILE\fR.
.PP
.PP
All informative, warning and error reports are sent to stderr so that
dd's output file can be stdout and remain unpolluted. If no options
are given, then no copying (nor reading) takes place and a brief message
is sent to stderr inviting the user to invoke ddpt again but with '\-\-help'
option to get the usage message.
.PP
Disk partition information can often be found with
.B fdisk(8)
[the "\-ul" argument is useful in this respect]. Also
.B parted(8)
can be used like this: 'parted /dev/sda unit s print' .
.PP
For pt devices this utility issues SCSI READ and WRITE (SBC) commands which
are appropriate for disks and reading from CD/DVD/BD drives. Those
commands are not formatted correctly for tape drives so ddpt cannot be
used on tape drives via a pt device. If the largest block address of the
requested transfer exceeds a 32 bit block number (i.e 0xffffffff) then a
warning is issued and the pt device is accessed via SCSI READ(16) and
WRITE(16) commands.
.PP
.B The attributes of a block device (e.g. partitions) are ignored when the
.B pt flag is used.
Hence the whole device is read (rather than just the second partition) by
this invocation:
.PP
   ddpt if=/dev/sdb2 iflag=pt of=t bs=512
.PP
Assuming /dev/sdb and /dev/sg2 refer to the same device, then after the
following two invocations, the contents of the files "t", "tt" and "ttt"
should be same:
.PP
   ddpt if=/dev/sdb of=tt bs=512
.PP
   ddpt if=/dev/sg2 of=ttt bs=512
.PP
The SCSI READ(32) and WRITE(32) commands are restricted to media that is
formatted with protection type 2. This is a T10 restriction.
.SH SIGNALS
The signal handling has been borrowed from GNU's dd: SIGINT, SIGQUIT and
SIGPIPE report the number of remaining blocks to be transferred and the
records in + out counts; then they have their default action. SIGUSR1 (or
SIGINFO) causes the same information to be output and the copy continues.
All output caused by signals is sent to stderr.
.PP
Like GNU's dd, ddpt respects the signal disposition of "ignored" (SIG_IGN)
set by the shell, script or other program that invokes ddpt. So in that
case it will ignore such signals. Further dd ignores SIGUSR1 if the
environment variable POSIXLY_CORRECT is set because POSIX defines dd will
only act on SIGINFO (and Linux has no such signal); ddpt ignores the
POSIXLY_CORRECT environment variable. As recommended by Susv3, ddpt does
not expect the signal (blocking) mask to be blocking SIGUSR1 (SIGINFO),
SIGINT or SIGPIPE on entry.
.PP
Unix system calls that do IO can be interrupted by signal processing,
typically returning an EINTR error number. The dd utility (and many other
Unix utilities) restart the IO operation that was interrupted. While
this will work most of the time for disk IO it is problematic for tape
drives because the implicit position pointer on the tape may have moved.
So the default (i.e. "intio=0") in this utility is to mask those signals
during IO operations and only check them prior to starting an IO operation.
Most low level IO (e.g. using SCSI command to write to a disk) will
timeout if there is a low level error. However NFS (the Network File
System) will potentially wait for a long time (e.g. expecting a network
problem will soon be fixed) and in this case using "intio=1" may be
best.
.SH TAPE
There is support for copies to and from tape drives in Linux. Only the st
driver device names can be used (e.g. /dev/st0 and /dev/nst2). Hence use of
Linux pass\-through device names (e.g. /dev/sg2) for tape drives is not
supported. On Debian\-based distributions, it is suggested that the mt\-st
package is installed as it provides a more fully\-featured version of
the "mt" tape control program.
.PP
Tape drives can operate in fixed\- or variable\-length block modes. In
variable\-block mode, each write to the tape writes a single block of that
size. In fixed\-block mode, each write to the tape must be a multiple of the
previously\-selected block size.
.PP
The block size/mode can be set with the mt command prior to invoking ddpt.
For example:
.br
  # mt \-f /dev/nst0 setblk 0
.br
sets variable\-block mode, and
.br
  # mt \-f /dev/nst0 setblk 32768
.br
sets fixed\-block mode with block size 32768 bytes.
.PP
Note that some tape drives support only fixed\-block mode, and possibly
even only one block size. (For example, QIC\-150 tapes use a fixed block
size of 512 bytes.) There may also be restrictions on the block size, e.g.
it may have to be even.
.PP
When using ddpt to write to tape, if the final read from the input is less
than \fIOBS\fR, it is padded to \fIOBS\fR bytes before writing to tape to
ensure that all blocks of the tape file are the same length. Having a
shorter final block would fail if the drive is in fixed\-block mode, and
could create interchange problems. It is common to expect all blocks in a
file on tape to be the same length. However, to tell ddpt to not pad the
final block, use 'oflag=nopad'.
.PP
The st tape driver normally writes a filemark when the file (e.g. /dev/nst0)
is closed. To not have the filemark written, use 'oflag=nofm'. One use case
for that might be if using ddpt several times in succession to append more
data to the same file on tape. In that case it is probably desirable to
write the filemark at the end of the sequence. So either omit 'oflag=nofm'
on the last ddpt invocation, or manually write a filemark using mt after
ddpt exits:
.br
  # mt \-f /dev/nst0 weof 1
.PP
For reading from an unknown tape where the block size(s) is not known, read
in variable\-block mode specifying a large \fIIBS\fR. The st driver returns
a smaller amount of data if the size of the block read is smaller. Thus a
command like:
.br
  # ddpt if=/dev/nst0 of=output.bin bs=262144
.br
should read the file from tape regardless of the block size used (assuming
no blocks are larger than 256KB). ddpt's verbose option will display what
the actual block size(s) is.
.SH ENVIRONMENT VARIABLES
If the command line invocation of an xcopy does not explicitly (and
unambiguously) indicate whether the XCOPY SCSI command should be sent
to \fIIFILE\fR (i.e.  the source) or \fIOFILE\fR (i.e. the destination)
then a check is made for the presence of the XCOPY_TO_SRC and
XCOPY_TO_DST environment variables. If either one exists (but not both)
then it indicates where the SCSI XCOPY command will be sent. By default
the XCOPY command is sent to \fIOFILE\fR.
.PP
The ODX write from tokens variant is very complex to implement if the amount
of data held in each ROD is not known. The value should be found in
the "number of bytes represented" field in the ROD Token but that is not well
supported yet by vendors. So for such case that number can be appended as a
big endian 8 byte integer following each ROD Token in the \fIRTF\fR file. The
\fIconv=rtf_len\fR will cause that length to be appended. Specifying that
option on each read to tokens and write from tokens invocation can be a
nuisance. Setting the environment variable ODX_RTF_LEN will cause this
utility to act as if the \fIconv=rtf_len\fR option has been given.
.SH EXIT STATUS
To aid scripts that call ddpt, the exit status is set to indicate
success (0) or failure (1 or more). Note that some of the lower values
correspond to the SCSI sense key values. The exit status values are:
.TP
.B 0
success
.TP
.B 1
syntax error. Either illegal command line options, options with bad
arguments or a combination of options that is not permitted.
.TP
.B 2
the device reports that it is not ready for the operation requested.
The device may be in the process of becoming ready (e.g.  spinning up but
not at speed) so the utility may work after a wait.
.TP
.B 3
the device reports a medium or hardware error (or a blank check). For example
an attempt to read a corrupted block on a disk will yield this value.
.TP
.B 5
the device reports an "illegal request" with an additional sense code other
than "invalid operation code". This is often a supported command with a
field set requesting an unsupported capability.
.TP
.B 6
the device reports a "unit attention" condition. This usually indicates
that something unrelated to the requested command has occurred (e.g. a
device reset) potentially before the current SCSI command was sent. The
requested command has not been executed by the device. Note that unit
attention conditions are usually only reported once by a device.
.TP
.B 9
the device reports an illegal request with an additional sense code
of "invalid operation code" which means that it doesn't support the
requested command.
.TP
.B 11
the device reports an aborted command. In some cases aborted commands can
be retried immediately (e.g. if the transport aborted the command due to
congestion).
.TP
.B 15
the utility is unable to open, close or use the given \fIIFILE\fR or
\fIOFILE\fR. The given file name could be incorrect or there may be
permission problems. Adding the \fI\-v\fR option may give more information.
.TP
.B 20
the device reports it has a check condition but "no sense".
It is unlikely that this value will occur as an exit status.
.TP
.B 21
the device reports a "recovered error". The requested command was successful.
Most likely a utility will report a recovered error to stderr and continue,
probably leaving the utility with an exit status of 0 .
.TP
.B 33
the command sent to device has timed out. This occurs in Linux only; in
other ports a command timeout will appear as a transport (or OS) error.
.TP
.B 51
a command received 'illegal field in parameter list'. This may occur with an
odx copy if some combination of parameters is illegal or not supported (e.g.
iflag=immed)
.TP
.B 55
a command received 'operation in progress'. This may occur with an odx copy
when the given \fILID\fR is already being used by another process (e.g. also
using odx) on the same machine. Choose another \fILID\fR.
.TP
.B 70
a command received 'invalid token operation, cause not reportable'. This may
occur with an odx operation when the given ROD Token is invalid. One reason
for that may be the inactivity timeout has been reached and the copy manager
has cancelled the ROD Token.
.TP
.B 71-89
these status values provide more information than exit status 70. See SPC\-4
ASC and ASCQ assignments (currently in Annex F.2), specifically the entries
for asc=23h . For example exit status 72 corresponds to asc=23h, ascq=2h
which implies the odx copy manager does not support copies between LUs in
different targets. That is optional; an odx copy manager is required to
support copies between LUs (that are block devices) in the same target.
.TP
.B 90
the flock flag has been given on a device and some other process holds the
advisory exclusive lock.
.TP
.B 97
the response to a SCSI command failed sanity checks.
.TP
.B 98
the device reports it has a check condition but the error doesn't fit into
any of the above categories.
.TP
.B 99
any errors that can't be categorized into values 1 to 98 may yield
this value. This includes transport and operating system errors
after the command has been sent to the device.
.SH EXAMPLES
The examples in this page use Linux device names. For suitable device
names in other supported Operating Systems see this web page:
http://sg.danny.cz/sg/device_name.html . The sg3_utils(8) man page
in the sg3_utils package also covers device naming.
.PP
ddpt usage looks quite similar to dd:
.PP
   ddpt if=/dev/sg0 of=t bs=512 count=1MB
.PP
This will copy 1 million 512 byte blocks from the device associated with
/dev/sg0 (which should have 512 byte blocks) to a file called t.
Assuming /dev/sda and /dev/sg0 are the same device then the above is
equivalent to:
.PP
   dd if=/dev/sda iflag=direct of=t bs=512 count=1000000
.PP
although dd's speed may improve if bs was larger and count was suitably
reduced. The use of the 'iflag=direct' option bypasses the buffering and
caching that is usually done on a block device.
.PP
The dd command's bs argument can be thought of as roughly equivalent to
ddpt's bs*bpt . dd almost assumes buffering on a block device and will
work as long as bs is a multiple of the actual logical block size.
Since ddpt can work at a lower level in some cases the bs argument must be
a disk's actual logical block size. Thus the bpt argument was introduced
to make the copy more efficient. So these two invocations are roughly
equivalent:
.PP
   dd if=/dev/sda of=t bs=8k count=64
.br
   ddpt if=/dev/sda of=t bs=512 bpt=16 count=1k
.PP
In both cases the total number of bytes moved is bs*count . And that will
be done by reading 8k (8192 bytes) into a buffer then writing out that
buffer to the file t. The read write sequence continues until the
count is complete or an error occurs.
.PP
The 'of2=' option can save time when the input would otherwise need to be
read twice. For example, to copy data and take a md5sum of it without
needing to re\-read the data:
.PP
  mkfifo fif
.br
  md5sum fif &
.br
  ddpt if=/dev/sg3 iflag=coe of=sg3.img oflag=sparse of2=fif bs=512
.PP
This will image /dev/sg3 (e.g. an unmounted disk) and place the contents
in the (sparse) file sg3.img . Without re\-reading the data it will also
perform a md5sum calculation on the image.
.PP
Now we use sparse writing logic to get some idea of how many blocks
on a disk are full of zeros. After a SCSI FORMAT UNIT command or an ATA
SECURITY ERASE command a disk may be all zeros.
.PP
   ddpt if=/dev/sdc bs=512 oflag=sparse
.PP
Since no "of=" option is given, output goes to /dev/null so nothing
is actually written so the "records out" will be zero. However there
will be a count of "records in" and "bypassed records out". If /dev/sdc is
full of zeros then "records in" and "bypassed records out" will be
the same. Since the "bpt=" option is not given it defaults to "bpt=128,128"
so the copy buffer will be 64 KiB and the sparse check for zeros will
be done with 64 KiB (128 block) granularity.
.PP
For examples of the trim and self,trim options see the section above
on TRIM, UNMAP AND WRITE SAME.
.PP
Following is an example run on a Windows OS using the '\-\-wscan' option
which shows the available device names (e.g. PD1) and the associated volume
name(s):
.PP
   ddpt \-w
.br
PD0     [C]     FUJITSU   MHY2160BH         0000
.br
PD1     [DF]    WD        2500BEV External  1.05  WD\-WXE90
.br
CDROM0  [E]     MATSHITA DVD/CDRW UJDA775  CB03
.PP
So, for example, volumes D: and F: reside on PhysicalDisk1 (abbreviated to
"PD1") which is manufactured by WD (Western Digital).
.PP
Further examples can be found on this web page:
http://sg.danny.cz/sg/ddpt.html . There is a text file containing examples
called ddpt_examples.txt in the "doc" directory of this package's
distribution tarball.
.SH AUTHORS
Written by Doug Gilbert
.SH "REPORTING BUGS"
Report bugs to <dgilbert at interlog dot com>.
.SH COPYRIGHT
Copyright \(co 2008\-2014 Douglas Gilbert
.br
This software is distributed under the GPL version 2. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
This utility has a companion/helper utility called
.B ddptctl(8)
.br
There is a web page discussing ddpt at http://sg.danny.cz/sg/ddpt.html
.PP
The lmbench package contains
.B lmdd
which is also interesting. For moving data to and from tapes see
.B dt
which is found at http://www.scsifaq.org/RMiller_Tools/index.html
.PP
To change mode parameters that effect a SCSI device's caching and error
recovery see
.B sdparm(sdparm)
.PP
To verify the data on the media or to verify it against some other
copy of the data see
.B sg_verify(sg3_utils)
.PP
To scan and repair disk partitions see TestDisk (testdisk).
.PP
Additional references:
.B dd(1), open(2), flock(2), sg_xcopy,sg_copy_results,
.B sg_dd(sg3_utils)