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SG_REASSIGN(8) SG3_UTILS SG_REASSIGN(8)
NAME
sg_reassign - send SCSI REASSIGN BLOCKS command
SYNOPSIS
sg_reassign [--address=A,A...] [--dummy] [--eight=0|1] [--grown] [--help] [--hex]
[--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 for-
matted 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 ad-
dresses. 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 logi-
cal block addresses.
OPTIONS
Arguments to long options are mandatory for short options as well. The options are ar-
ranged in alphabetical order based on the long option name.
-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 mul-
tiple 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 char-
acters should resolve to a decimal number unless prefixed by '0x' or '0X' (or has a
trailing 'h'). At least one address must be given. Lines should not be longer than
1023 bytes.
-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 --ad-
dress= option is not permitted. See the discussion below concerning the relation-
ship 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.
-H, --hex
print response in hex (for -g, --grown, -p or --primary).
-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 au-
tomatic 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). Irre-
spective 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 recover-
able 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 spe-
cific 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 (C) 2005-2019 Douglas Gilbert
This software is distributed under a FreeBSD license. There is NO warranty; not even for
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
SEE ALSO
sg_format,sginfo,sg_senddiag(all in sg3_utils), sdparm(sdparm), smartmontools(internet,
sourceforge)
sg3_utils-1.45 October 2019 SG_REASSIGN(8)
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