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.TH SG_VERIFY "8" "June 2006" "sg3_utils-1.21" SG3_UTILS
.SH NAME
sg_verify \- invoke SCSI VERIFY command(s) on a block device
.SH SYNOPSIS
.B sg_verify
[\fI--bpc=<n>\fR] [\fI--count=<n>\fR] [\fI--dpo\fR] [\fI--help\fR]
[\fI--lba=<n>\fR] [\fI--verbose\fR] [\fI--version\fR]
\fI<scsi_device>\fR
.SH DESCRIPTION
.\" Add any additional description here
.PP
Sends one or more SCSI VERIFY commands to the given Linux SCSI device.
It is a 10 byte VERIFY command defined for block devices (see SBC-2
at http://www.t10.org). Verify starts at the logical block address
given by the '--lba=<n>' option and continues for '--count=<n>'
blocks. No more than '--bpc=<n>' blocks are verified by each VERIFY
command so if necessary multiple VERIFY commands are sent.
No news is good news (i.e. if there are no verify errors detected
no messages are sent to stderr and the Unix return status is 0).
.TP
--bpc=<n> | -b <n>
specifies the maximum number of blocks that will be verified by a
single SCSI VERIFY command. The default value is 128 blocks which
equates to 64 KB for a disk with 512 byte blocks. If the value <n>
is less than the value given to --count then multiple SCSI VERIFY
commands are sent to the device. For recent block devices (disks)
this value may be constrained by the maximum transfer length field
in the block limits VPD page.
.TP
--dpo | -d
disable page out changes the cache retention priority of blocks read on
the device's cache to the lowest priority. This means that blocks read by
other commands are more likely to remain in the device's cache.
.TP
--count=<n> | -c <n>
specifies the number of blocks to verify. The default value is 1 .
If <n> is greater than the value associated with '--bpc' (or its default
value of 128) then multiple SCSI VERIFY commands are sent to the
device. The
.B sg_readcap
utility can be used to find the maximum number of blocks that a block
device (e.g. a disk) has.
.TP
--help | -h
output the usage message then exit.
.TP
--lba=<n> | -l <n>
specifies the logical block address on the device to start the verify
operation. <n> is assumed to be decimal unless prefixed by '0x' or
a trailing 'h' (see below). The default value is 0 (i.e. the start of the
device).
.TP
--verbose | -v
increase the level of verbosity, (i.e. debug output).
.TP
--version | -V
print the version string and then exit.
.PP
The arguments to --bpc, --count and --lba may be followed by one of these
multiplicative suffixes:
c C *1; w W *2; b B *512; k K KiB *1,024; KB *1,000; m M MiB *1,048,576;
MB *1,000,000; g G GiB *1,073,741,824; GB *1,000,000,000; t T TiB *(2**40);
TB *(10**12); p P PiB *(2**50) and PB *(10**15). The "T" and "P" based
suffixes can only be used for --count and --lba. Also a suffix of the
form "x<n>" multiplies the leading number by <n>.
.PP
Alternatively numerical values can be given in hexadecimal preceded by
either "0x" or "0X" (or has a trailing "h" or "H"). When hex numbers are
given, multipliers cannot be used.
.PP
The amount of error correction and the number of retries attempted
before a block is considered defective are controlled in part by the
Verify Error Recovery mode page. A note in the SBC-2 (draft)
standard advises that to minimize the number of checks (and hence
have the most "sensitive" verify check) do the following in that
mode page. Set the EER bit to 0, the PER bit to 1, the DTE bit to 1,
the DCR bit to 1, the verify retry count to 0 and the verify error
recovery timeout to 0. Mode pages can be modified with the
.B sginfo
utility.
.SH EXIT STATUS
The exit status of sg_verify is 0 when it is successful. Otherwise see
the sg3_utils(8) man page.
.SH AUTHORS
Written by Douglas Gilbert.
.SH "REPORTING BUGS"
Report bugs to <dgilbert at interlog dot com>.
.SH COPYRIGHT
Copyright \(co 2004-2006 Douglas Gilbert
.br
This software is distributed under a FreeBSD license. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
.SH "SEE ALSO"
.B sginfo(sg3_utils), sg_modes(sg3_utils), sg_readcap(sg3_utils),
.B sg_inq(sg3_utils)
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