phpMan > man > sg_test_rwbuf(8)

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 un‐
       equal)  then  this  is  reported  and up to 24 bytes from the first point of mismatch are re‐
       ported; 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  buf‐
              fer. 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 num‐
              ber  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 re‐
       spect. [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 © 2000-2018 Douglas Gilbert, Kurt Garloff
       This software is distributed under the GPL version 2. There is NO warranty; not even for MER‐
       CHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.



sg3_utils-1.43                              January 2018                            SG_TEST_RWBUF(8)