1SG_TEST_RWBUF(8)                   SG3_UTILS                  SG_TEST_RWBUF(8)
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NAME

6       sg_test_rwbuf  -  test  a SCSI host adapter by issuing dummy writes and
7       reads
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SYNOPSIS

10       sg_test_rwbuf [--addrd=AR] [--addwr=AW]  [--help]  [--quick]  --size=SZ
11       [--times=NUM] [--verbose] [--version] DEVICE
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13       or an older deprecated format sg_test_rwbuf DEVICE SZ [AW] [AR]
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DESCRIPTION

16       sg_test_rwbuf  writes and reads back SZ bytes to the internal buffer of
17       DEVICE (e.g. /dev/sda or /dev/sg0). A pseudo random pattern is  written
18       to the data buffer on the device then read back. If the same pattern is
19       found 'Success' is reported. If they do not match  (checksums  unequal)
20       then  this  is reported and up to 24 bytes from the first point of mis‐
21       match are reported; the first line shows what was written and the  sec‐
22       ond  line shows what was received. For testing purposes, you can ask it
23       to write AW or read AR additional bytes.
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OPTIONS

26       Arguments to long options are mandatory for short options as well.
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28       -r, --addrd=AR
29              Read an additional AR bytes (than indicated by SZ) from the data
30              buffer. Checksum is performed over the first SZ bytes.
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32       -w, --addwr=AW
33              Write  an  additional  AW  bytes (than indicated by SZ) of zeros
34              into the data buffer. Checksum is generated over  the  first  SZ
35              bytes.
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37       -h, --help
38              Print out a usage message the exit.
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40       -q, --quick
41              Perform  a READ BUFFER descriptor command to find out the avail‐
42              able data buffer length and offset, print  them  out  then  exit
43              (without testing with write/read sequences).
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45       -s, --size=SZ
46              where  SZ is the size of buffer in bytes to be written then read
47              and checked. This number needs to be less than or equal  to  the
48              size  of  the  device's  data  buffer which can be seen from the
49              --quick option.  Either this option or the --quick option should
50              be given.
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52       -t, --times=NUM
53              where  NUM  is  the  number of times to repeat the write/read to
54              buffer test. Default value is 1 .
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56       -v, --verbose
57              increase verbosity of output.
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59       -V, --version
60              print version number (and data of last change) then exit.
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NOTES

63       The microcode in a SCSI device is _not_ modified by doing a WRITE  BUF‐
64       FER  command with its mode set to "data" (0x2) as done by this utility.
65       Therefore this utility is safe in that respect. [Mode values 0x4,  0x5,
66       0x6 and 0x7 are the dangerous ones :-)]
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68       WARNING: If you access the device at the same time (e.g. because it's a
69       hard disk with a mounted file system on it) the device's buffer may  be
70       used  by  the  device itself for other data at the same time, and over‐
71       writing it may or may not cause  data  corruption!  HOWEVER  the  SPC-3
72       draft  standard  does  state in its WRITE BUFFER command: "This command
73       shall not alter any medium of the logical unit when data  mode  ...  is
74       specified".  This  implies  that  it _is_ safe to use this utility with
75       devices that have mounted file systems on them.  Following  this  theme
76       further,  a  disk  with  active mounted file systems may cause the data
77       read back to be different (due to caching activity) to what was written
78       and hence a checksum error.
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EXIT STATUS

81       The  exit status of sg_test_rwbuf is 0 when it is successful. Otherwise
82       see the sg3_utils(8) man page.
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AUTHORS

85       Written by D. Gilbert and K. Garloff
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88       Copyright © 2000-2012 Douglas Gilbert, Kurt Garloff
89       This software is distributed under the GPL version 2. There is NO  war‐
90       ranty;  not  even  for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
91       POSE.
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95sg3_utils-1.35                   November 2012                SG_TEST_RWBUF(8)
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