SG_VERIFY(8)							     SG3_UTILS							      SG_VERIFY(8)

NAME

       sg_verify - invoke SCSI VERIFY command(s) on a block device

SYNOPSIS

       sg_verify [--bpc=BPC] [--count=COUNT] [--dpo] [--help] [--lba=LBA] [--readonly] [--verbose] [--version] [--vrprotect=VRP] DEVICE

DESCRIPTION

       Sends  one  or  more  SCSI  VERIFY  commands  to  DEVICE.  It  is  the  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=LBA option and continues for --count=COUNT  blocks.	No
       more  than  --bpc=BPC  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).

OPTIONS

       Arguments to long options are mandatory for short options as well.  The options are arranged in alphabetical order based on the long option
       name.

       -b, --bpc=BPC
	      where  BPC  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 BPC is less than 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 lim-
	      its VPD page.

       -c, --count=COUNT
	      where COUNT specifies the number of blocks to verify. The default value is 1 . If COUNT is greater than BPC (or its default value of
	      128)  then  multiple  SCSI  VERIFY commands are sent to the device. The sg_readcap utility can be used to find the maximum number of
	      blocks that a block device (e.g. a disk) has.

       -d, --dpo
	      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.

       -h, --help
	      output the usage message then exit.

       -l, --lba=LBA
	      where  LBA specifies the logical block address of the first block to start the verify operation. LBA 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).   -r,  --readonly	opens  the
	      DEVICE  read-only  rather than read-write which is the default. The Linux sg driver needs read-write access for the SCSI VERIFY com-
	      mand but other access methods may require read-only access.

       -v, --verbose
	      increase the level of verbosity, (i.e. debug output).

       -V, --version
	      print the version string and then exit.

       -P, --vrprotect=VRP
	      where VRP is the value in the vrprotect field in the VERIFY command cdb. It must be a value between 0 and 7 inclusive.  The  default
	      value is zero.

NOTES

       Various numeric arguments (e.g. LBA) may include multiplicative suffixes or be given in hexadecimal. See the "NUMERIC ARGUMENTS" section in
       the sg3_utils(8) man page.

       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 sginfo utility.

EXIT STATUS

       The exit status of sg_verify is 0 when it is successful. Otherwise see the sg3_utils(8) man page.

AUTHORS

       Written by Douglas Gilbert.

REPORTING BUGS

       Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT

       Copyright (C) 2004-2011 Douglas Gilbert
       This  software  is distributed under a FreeBSD license. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR-
       POSE.

SEE ALSO

       sginfo(sg3_utils), sg_modes(sg3_utils), sg_readcap(sg3_utils), sg_inq(sg3_utils)

sg3_utils-1.31							   February 2011						      SG_VERIFY(8)