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SG_TEST_RWBUF(8) SG3_UTILS SG_TEST_RWBUF(8)
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] [--ver-
bose] [--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 mis-
match 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 (more than indicated by SZ) from the data buffer.
Checksum is performed over the first SZ bytes.
-w, --addwr=AW
Write an additional AW bytes (more 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 se-
quences).
-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 check-
sum 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 (C) 2000-2018 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.
sg3_utils-1.43 January 2018 SG_TEST_RWBUF(8)
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