sg_reassign - send SCSI REASSIGN BLOCKS command
] [ --grown
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
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
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
up of 8 byte logical block addresses.
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. 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 --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.
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
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.
The exit status of sg_reassign is 0 when it is successful. Otherwise see the
sg3_utils(8) man page.
Written by Douglas Gilbert.
Report bugs to <dgilbert at interlog dot com>.
Copyright © 2005-2014 Douglas Gilbert
This software is distributed under a FreeBSD license. There is NO warranty; not
even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
sg_format,sginfo,sg_senddiag(all in sg3_utils), sdparm(sdparm),