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
              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 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)