NAME¶
sg_test_rwbuf - test a SCSI host adapter by issuing dummy writes and reads
SYNOPSIS¶
sg_test_rwbuf [
--addrd=AR] [
--addwr=AW] [
--help] [
--quick]
--size=SZ [
--times=NUM] [
--verbose] [
--version]
DEVICE
or an older deprecated format
sg_test_rwbuf DEVICE SZ
[
AW] [
AR]
DESCRIPTION¶
sg_test_rwbuf writes and reads back
SZ bytes to the internal buffer of
DEVICE (e.g. /dev/sda or /dev/sg0). A pseudo random pattern is written
to the data buffer on the device then read back. If the same pattern is found
'Success' is reported. If they do not match (checksums unequal) then this is
reported and up to 24 bytes from the first point of mismatch are reported; the
first line shows what was written and the second line shows what was received.
For testing purposes, you can ask it to write
AW or read
AR
additional bytes.
OPTIONS¶
Arguments to long options are mandatory for short options as well.
- -r, --addrd=AR
- Read an additional AR bytes (than indicated by SZ) from the
data buffer. Checksum is performed over the first SZ bytes.
- -w, --addwr=AW
- Write an additional AW bytes (than indicated by SZ) of zeros
into the data buffer. Checksum is generated over the first SZ
bytes.
- -h, --help
- Print out a usage message the exit.
- -q, --quick
- Perform a READ BUFFER descriptor command to find out the available data
buffer length and offset, print them out then exit (without testing with
write/read sequences).
- -s, --size=SZ
- where SZ is the size of buffer in bytes to be written then read and
checked. This number needs to be less than or equal to the size of the
device's data buffer which can be seen from the --quick option.
Either this option or the --quick option should be given.
- -t, --times=NUM
- where NUM is the number of times to repeat the write/read to buffer
test. Default value is 1 .
- -v, --verbose
- increase verbosity of output.
- -V, --version
- print version number (and data of last change) then exit.
NOTES¶
The microcode in a SCSI device is _not_ modified by doing a WRITE BUFFER command
with its mode set to "data" (0x2) as done by this utility. Therefore
this utility is safe in that respect. [Mode values 0x4, 0x5, 0x6 and 0x7 are
the dangerous ones :-)]
WARNING: If you access the device at the same time (e.g. because it's a
hard disk with a mounted file system on it) the device's buffer may be used by
the device itself for other data at the same time, and overwriting it may or
may not cause data corruption!
HOWEVER the SPC-3 draft standard does
state in its WRITE BUFFER command: "This command shall not alter any
medium of the logical unit when data mode ... is specified". This implies
that it _is_ safe to use this utility with devices that have mounted file
systems on them. Following this theme further, a disk with active mounted file
systems may cause the data read back to be different (due to caching activity)
to what was written and hence a checksum error.
EXIT STATUS¶
The exit status of sg_test_rwbuf is 0 when it is successful. Otherwise see the
sg3_utils(8) man page.
AUTHORS¶
Written by D. Gilbert and K. Garloff
COPYRIGHT¶
Copyright © 2000-2012 Douglas Gilbert, Kurt Garloff
This software is distributed under the GPL version 2. There is NO warranty; not
even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.