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.TH SG_VERIFY "8" "February 2011" "sg3_utils\-1.31" SG3_UTILS
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.TH SG_VERIFY "8" "December 2012" "sg3_utils\-1.35" SG3_UTILS
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sg_verify \- invoke SCSI VERIFY command(s) on a block device
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[\fI\-\-bpc=BPC\fR] [\fI\-\-count=COUNT\fR] [\fI\-\-dpo\fR] [\fI\-\-help\fR]
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[\fI\-\-16\fR] [\fI\-\-bpc=BPC\fR] [\fI\-\-bytchk=NDO\fR]
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[\fI\-\-count=COUNT\fR] [\fI\-\-dpo\fR] [\fI\-\-ebytchk=BVAL\fR]
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[\fI\-\-group=GN\fR] [\fI\-\-help\fR] [\fI\-\-in=IF\fR]
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[\fI\-\-lba=LBA\fR] [\fI\-\-readonly\fR] [\fI\-\-verbose\fR]
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[\fI\-\-version\fR] [\fI\-\-vrprotect=VRP\fR] \fIDEVICE\fR
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[\fI\-\-version\fR] [\fI\-\-vrprotect=VRP\fR]
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.\" Add any additional description here
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Sends one or more SCSI VERIFY commands to \fIDEVICE\fR. It is the 10 byte
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VERIFY command defined for block devices (see SBC\-2 at http://www.t10.org).
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Verify starts at the logical block address given by the \fI\-\-lba=LBA\fR
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option and continues for \fI\-\-count=COUNT\fR blocks. No more than
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\fI\-\-bpc=BPC\fR blocks are verified by each VERIFY command so if necessary
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multiple VERIFY commands are sent. No news is good news (i.e. if there are
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no verify errors detected no messages are sent to stderr and the Unix return
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Sends one or more SCSI VERIFY (10 or 16) commands to \fIDEVICE\fR. These SCSI
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commands are defined in the SBC\-2 (draft) standard at http://www.t10.org and
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When \fI\-\-bytchk=NDO\fR is not given then the verify starts at the logical
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block address given by the \fI\-\-lba=LBA\fR option and continues for
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\fI\-\-count=COUNT\fR blocks. No more than \fI\-\-bpc=BPC\fR blocks are
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verified by each VERIFY command so if necessary multiple VERIFY commands are
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sent. No news is good news (i.e. if there are no verify errors detected then
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no messages are sent to stderr and the Unix return status is 0).
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When \fI\-\-bytchk=NDO\fR is given then the \fI\-\-bpc=BPC\fR option is
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ignored. A single verify command is issued and it starts at the logical block
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address given by the \fI\-\-lba=LBA\fR option and continues for
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\fI\-\-count=COUNT\fR blocks. The VERIFY command has an associated data\-out
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buffer that is \fINDO\fR bytes long. The contents of the data\-out buffer are
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obtained from the \fIFN\fR file (if \fI\-\-in=FN\fR is given) or from stdin.
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Arguments to long options are mandatory for short options as well.
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The options are arranged in alphabetical order based on the long
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\fB\-S\fR, \fB\-\-16\fR
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uses a VERIFY(16) command (default VERIFY(10)). Even without this option,
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using an \fI\-\-lba=LBA\fR which is too large, will cause the utility
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to issue a VERIFY(16) command.
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\fB\-b\fR, \fB\-\-bpc\fR=\fIBPC\fR
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where \fIBPC\fR specifies the maximum number of blocks that will be verified
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by a single SCSI VERIFY command. The default value is 128 blocks which
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equates to 64 KB for a disk with 512 byte blocks. If \fIBPC\fR is less than
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\fICOUNT\fR then multiple SCSI VERIFY commands are sent to the device. For
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recent block devices (disks) this value may be constrained by the maximum
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transfer length field in the block limits VPD page.
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this option is ignored if \fI\-\-bytchk=NDO\fR is given. Otherwise \fIBPC\fR
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specifies the maximum number of blocks that will be verified by a single SCSI
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VERIFY command. The default value is 128 blocks which equates to 64 KB for a
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disk with 512 byte blocks. If \fIBPC\fR is less than \fICOUNT\fR then
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multiple SCSI VERIFY commands are sent to the device. For the default
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VERIFY(10) \fIBPC\fR cannot exceed 0xffff (65,535) while for VERIFY(16)
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\fIBPC\fR cannot exceed 0x7fffffff (2,147,483,647). For recent block
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devices (disks) this value may be constrained by the maximum transfer length
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field in the block limits VPD page.
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\fB\-B\fR, \fB\-\-bytchk\fR=\fINDO\fR
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sets the BYTCHK field to one in the VERIFY command. \fINDO\fR is the number
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of bytes to obtain from the \fIFN\fR file (if \fI\-\-in=FN\fR is given) or
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from stdin. Those bytes are placed in the data\-out buffer associated with
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the SCSI VERIFY command. The minimum value for \fINDO\fR is 1 and the
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maximum value is dependant on the OS. The actual value in the BYTCHK field
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in the VERIFY command may be modified by a \fI\-\-ebytchk=BVAL\fR option.
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\fB\-c\fR, \fB\-\-count\fR=\fICOUNT\fR
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where \fICOUNT\fR specifies the number of blocks to verify. The default value
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is 1 . If \fICOUNT\fR is greater than \fIBPC\fR (or its default value of 128)
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then multiple SCSI VERIFY commands are sent to the device. The
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and \fINDO\fR is not given, 0 or less then multiple SCSI VERIFY commands are
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sent to the device. Otherwise \fICOUNT\fR becomes the contents of the
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verification length field of the SCSI VERIFY command issued. The
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utility can be used to find the maximum number of blocks that a block
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device (e.g. a disk) has.
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the device's cache to the lowest priority. This means that blocks read by
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other commands are more likely to remain in the device's cache.
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\fB\-E\fR, \fB\-\-ebytchk\fR=\fIBVAL\fR
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sets the BYTCHK field to \fIBVAL\fR overriding the value (1) set by the
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\fI\-\-bytchk=NDO\fR option. Values of 1, 2 or 3 are accepted for \fIBVAL\fR
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however sbc3r34 reserves the value 2. If this option is given then
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\fI\-\-bytchk=NDO\fR must also be given. If \fIBVAL\fR is 3 then \fICOUNT\fR
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must be 1 and \fINDO\fR should be the size of one logical block (plus the
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size of some or all of the protection infomation if \fIVRP\fR is greater
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\fB\-g\fR, \fB\-\-group\fR=\fIGN\fR
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where \fIGN\fR becomes the contents of the group number field in the SCSI
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VERIFY(16) command. The default value for \fIGN\fR is 0. Note that this
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option is ignored for the SCSI VERIFY(10) command.
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\fB\-h\fR, \fB\-\-help\fR
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output the usage message then exit.
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\fB\-i\fR, \fB\-\-in\fR=\fIIF\fR
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where \fIIF\fR is the name of a file from which \fINDO\fR bytes will be read
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and placed in the data\-out buffer. This is only done when the
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\fI\-\-bytchk=NDO\fR option is given. If this option is not given then stdin
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is read. If \fIIF\fR is "\-" then stdin is also used.
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\fB\-l\fR, \fB\-\-lba\fR=\fILBA\fR
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where \fILBA\fR specifies the logical block address of the first block to
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start the verify operation. \fILBA\fR is assumed to be decimal unless prefixed
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where \fIVRP\fR is the value in the vrprotect field in the VERIFY command
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cdb. It must be a value between 0 and 7 inclusive. The default value is
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BYTCHK is the name of a field (two bits wide) in the VERIFY(10) and
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VERIFY(16) commands. When set to 1 or 3 (sbc3r34 reserves the value 2) it
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indicates that associated with the SCSI VERIFY command, a data\-out buffer
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will be sent for the device (disk) to check. Using the \fI\-\-bytchk=NDO\fR
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option sets the BYTCHK field to 1 and \fINDO\fR is the number of bytes
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placed in the data\-out buffer. Those bytes are obtained from stdin or
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\fIIF\fR (from the \fI\-\-in=FN\fR option). The \fI\-\-ebytchk=BVAL\fR
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option may be used to override the BYTCHK field value of 1 with \fIBVAL\fR.
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The calculation of \fINDO\fR is left up to the user. Its value depends
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on the logical block size (which cab be found with the sg_readcap utility),
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the \fICOUNT\fR and the \fIVRP\fR values. If the \fIVRP\fR is greater than
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0 then each logical block will contain an extra 8 bytes (at least) of
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protection information.
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When the BYTCHK field is 0 then the verification process done by the
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device (disk) is vendor specific. It typically involves checking each
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block on the disk against its error correction codes (ECC) which is
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additional data also held on the disk.
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Many Operating Systems put limits on the maximum size of the
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data\-out (and data\-in) buffer. For Linux at one time the limit was
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less than 1 MB but has been increased somewhat.
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Various numeric arguments (e.g. \fILBA\fR) may include multiplicative
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suffixes or be given in hexadecimal. See the "NUMERIC ARGUMENTS" section
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in the sg3_utils(8) man page.
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The amount of error correction and the number of retries attempted
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before a block is considered defective are controlled in part by the
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Verify Error Recovery mode page. A note in the SBC\-2 (draft)
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standard advises that to minimize the number of checks (and hence
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have the most "sensitive" verify check) do the following in that
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mode page. Set the EER bit to 0, the PER bit to 1, the DTE bit to 1,
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the DCR bit to 1, the verify retry count to 0 and the verify error
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recovery timeout to 0. Mode pages can be modified with the
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The amount of error correction and the number of retries attempted before a
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block is considered defective are controlled in part by the Verify Error
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Recovery mode page. A note in the SBC\-3 draft (rev 29 section 6.4.9 on the
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Verify Error Recovery mode page) advises that to minimize the number of
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checks (and hence have the most "sensitive" verify check) do the following
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in that mode page: set the EER bit to 0, the PER bit to 1, the DTE bit to 1,
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the DCR bit to 1, the verify retry count to 0 and the verify recovery time
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limit to 0. Mode pages can be modified with the
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The SCSI VERIFY(6) command defined in the SSC\-2 standard and later (i.e.
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for tape drive systems) is not supported by this utility.
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The exit status of sg_verify is 0 when it is successful. Otherwise see
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the sg3_utils(8) man page.
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doc/sg_verify.8
