NAME¶
sraw - benchmark raw scsi I/O performance under linux
SYNOPSIS¶
sraw [
-fiv6 ]
scsi-device [
bstart [
bstep ]
]
DESCRIPTION¶
This program basically reads the specified scsi device and measures the
throughput. Note that the filesystem *AND* the buffer cache are bypassed by
this code, this program was designed to benchmark the naked scsi drivers by
themselves without the need to account for the overhead of any other portion
of the kernel. It also could be used to benchmark disk read throughput.
This program does a series of reads of the disk, of consecutive areas on the
disk. The device is first queried to determine the sector size for the device,
and then the series of reads is begun. About 5.0 Mb is read from the device,
and then the performance numbers are reported. Note that since the buffer
cache is completely bypassed, there is no need to be concerned about cache
hits or anything.
Output of
sraw is a set of lines, 4 numbers per line:
blocksize,
elapsed time, nblocks and
throughput (in bytes per second).
scsi-device is either a block device (e.g. /dev/sda, /dev/scd0) or a
generic SCSI device (e.g. /dev/sg0).
OPTIONS¶
- -f
- set FUA (Force Unit Access) bit during read. Data is then read from media
instead of internal drive cache.
- -i
- use legacy ioctl instead of new SG I/O layer (will not work on 2.6 kernel
and block devices).
- -v
- more verbose output.
- -6
- use 6-bytes instead of 10-bytes read command. In this case, only the first
GB of data could be read from media.
- bstart
- starting block to check different zones on ZBR discs
- bstep
- factor for sequential stepping, default 1. Use 0 for reading always the
same blocks (from cache)
ERRORS¶
sraw could issue input/output errors when reading too many blocks at the
same time from a block device like /dev/sda. To get rid of them, use /dev/sgN
instead.
AUTHOR¶
sraw was first written by Eric Youngdale. Extensions (-v, -f, -6, SG IO,
man page) were written by Eric Delaunay.
SEE ALSO¶
sg_dd(8) from sg3-utils package.
AVAILABILITY¶
sraw is available at
ftp://tsx-11.mit.edu/pub/linux/ALPHA/scsi/