Ubuntu Manpage: sg_reassign - send SCSI REASSIGN BLOCKS command

Provided by: sg3-utils_1.36-1ubuntu1_amd64

NAME

       sg_reassign - send SCSI REASSIGN BLOCKS command

SYNOPSIS

       sg_reassign  [--address=A,A...]  [--dummy]  [--eight=0|1] [--grown] [--help] [--longlist=0|1] [--primary]
       [--verbose] [--version] DEVICE

DESCRIPTION

       Send a SCSI REASSIGN BLOCKS command to DEVICE. Alternatively this utility can find the number of  element
       in  a "grown" or "primary" defect list with a SCSI READ DEFECT DATA (10) command. These SCSI commands are
       defined in SBC-2 for direct access devices (e.g. a disk). Reassign  blocks  is  designed  to  change  the
       physical  location  of  a logical block that is known or suspected to be defective to another area on the
       media. Disks are typically formatted with blocks held in reserve for this situation.

       If neither the --grown nor --primary option is supplied then one or more addresses need to be  given.  If
       the  address  (or  all of the addresses) fit into 4 bytes and '--eight=1' is not given then the parameter
       block passed to DEVICE is made up of 4 byte logical block addresses. If any of the  addresses  need  more
       than  4  bytes  to  represent  (i.e. >= 2**32) or '--eight=1' is given then the parameter block passed to
       DEVICE is made up of 8 byte logical block addresses.

OPTIONS

Arguments to long options are mandatory for short options as well.

-a, --address=A,A...
where A,A... is a string of comma separated numbers. Each number is interpreted as decimal unless
prefixed by '0x' or '0X' (or it has a trailing 'h' or 'H'). If multiple logical block addresses
are given they must be separated by a comma or a (single) space. A string that contains any space
separators needs to be quoted. At least one address must be given.

-a, --address=-
reads one or more logical block addresses from stdin. These may be comma, space, tab or linefeed
(newline) separated. If a line contains "#" then the remaining characters on that line are
ignored. Otherwise each non separator sequence of characters should resolve to a decimal number
unless prefixed by '0x' or '0X' (or has a trailing 'h'). At least one address must be given.

-d, --dummy
prepare for but do not execute the SCSI REASSIGN BLOCKS command. Since the REASSIGN BLOCKS command
is essentially irreversible, paranoid users may wish to check the invocation of this utility
before reassigning defective blocks on a disk. Useful with '-vv' for those who wish to view the
parameter block that will accompany the command.

-e, --eight=0 | 1
when value is 1 then it sets the 'LONGLBA' flag in the command indicating that the addresses in
the associated parameter block are 8 byte quantities. When value is 0 then it clears the
'LONGLBA' flag in the command indicating that the addresses in the associated parameter block are
4 byte quantities. If this option is not given then 4 byte quantities are assumed unless one of
the address is too large.

-g, --grown
use the SCSI READ DEFECT DATA (10) command to determine the number of elements in the "grown
defect list". When this option is given there is no reassignment of blocks (i.e. this utility is
passive). When this option is given then the --address= option is not permitted. See the
discussion below concerning the relationship between reassigned blocks and the grown defect list.
This list is sometimes referred to as the GLIST.

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

-l, --longlist=0 | 1
sets the REASSIGN BLOCKS cdb field of the same name to the given value. Only 1000 addresses are
permitted so there should be no need to specify a value of 1. The short list variant restricts the
parameter block length to 2 ** 16 bytes (i.e. about 16000 4 byte addresses or 8000 8 byte
addresses). Added for completeness.

-p, --primary
use the SCSI READ DEFECT DATA (10) command to determine the number of elements in the "primary
defect list" which is established during the manufacturing process. When this option is given
there is no reassignment of blocks (i.e. this utility is passive). When this option is given then
the --address= option is not permitted. This list is sometimes referred to as the PLIST.

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

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

NOTES

Note that if the ARRE field (for reads) and/or the AWRE field (for writes) are set in the "Read Write
Error Recovery" mode page then recoverable read and/or write errors cause automatic reassignment of the
defective block. The PER bit in the same mode page controls whether a RECOVERED ERROR sense key is
reported on not (PER=1 implies do report). Irrespective of the ARRE, AWRE or PER field settings, the
error counter log pages reflect any errors (recovered or otherwise). Whenever a block is reassigned, a
new entry is added in the "grown" defect list. Apart from doing selftests (see sg_senddiag or
smartmontools) regularly, monitoring the grown defect list of a disk is a reasonable metric of its
health. If the grown list starts growing quickly that is an ominous sign. The best grown defect lists are
empty ones. The number of elements in the grown defect list can be viewed with the --grown option. The
contents of the grown defect list can be viewed with the 'sginfo -G' utility.

If an unrecoverable error is detected at a logical block address then REASSIGN BLOCKS is needed to
reassign the block. Also if the ARRE and/or AWRE fields are clear and a recoverable error is detected
then the logical block in question may be reassigned with this utility (otherwise the error counter log
pages will continually be incremented for each recovered access).

The number of blocks held in reserve for the purposes of REASSIGN BLOCKS is vendor specific and may well
be limited to the zone within the media where the original (defective) block lay. When this number is
exhausted subsequent invocations of this utility may result in a sense key of hardware error and an
additional sense of 'No defect spare location available'. The next step would be to reformat the disk (or
get a replacement).

The SBC-2 draft standard (revision 16) notes that when multiple addresses are given to the SCSI REASSIGN
BLOCKS command and there is some failure at one of the later addresses then all addresses prior to that
have already be reassigned. Care should be taken in such a case. Re-executing the command with the same
addresses will cause the earlier addresses to be reassigned again. At some stage the disk will run out of
reserved locations. So unless a large number of addresses are involved it may be safer to reassign them
one address at a time.

EXIT STATUS

       The exit status of sg_reassign 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 © 2005-2012 Douglas Gilbert
       This  software is distributed under a FreeBSD license. There is NO warranty; not even for MERCHANTABILITY
       or FITNESS FOR A PARTICULAR PURPOSE.