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.