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man pages section 8: System Administration Commands

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Updated: Wednesday, February 9, 2022
 
 

sg_unmap (8)

Name

sg_unmap - send SCSI UNMAP command (known as 'trim' in ATA specs)

Synopsis

sg_unmap  [--all=ST,RN[,LA]]  [--anchor]  [--dry-run] [--force] [--grp-
num=GN]  [--help]  [--in=FILE]  [--lba=LBA,LBA...]   [--num=NUM,NUM...]
[--timeout=TO] [--verbose] [--version] DEVICE

Description

SG_UNMAP(8)                        SG3_UTILS                       SG_UNMAP(8)



NAME
       sg_unmap - send SCSI UNMAP command (known as 'trim' in ATA specs)

SYNOPSIS
       sg_unmap  [--all=ST,RN[,LA]]  [--anchor]  [--dry-run] [--force] [--grp-
       num=GN]  [--help]  [--in=FILE]  [--lba=LBA,LBA...]   [--num=NUM,NUM...]
       [--timeout=TO] [--verbose] [--version] DEVICE

DESCRIPTION
       Send  a  SCSI  UNMAP  command  to  DEVICE  to unmap one or more logical
       blocks. This command was introduced in  SBC-3  revision  18  under  the
       broad  heading of "logical block provisioning". Logical blocks may also
       be unmapped by the SCSI WRITE SAME command; see the sg_write_same util-
       ity.  The  unmap capability is closely related to the ATA DATA SET MAN-
       AGEMENT command with the "Trim" bit set.

       Logical blocks to be unmapped can be specified in one of three ways  to
       this  utility.  One  way is by supplying the start LBAs to the '--lba='
       option and the corresponding number(s) to unmap to the '--num=' option.
       Another way is by putting start LBA and number to unmap pairs in a file
       whose name is given to the '--in=' option. Alternatively a  large  seg-
       ment  or  all of a disk (SSD) can be unmapped with the --all=ST_RN[,LA]
       option. All values are assumed to be decimal unless  prefixed  by  "0x"
       (or "0X") or have a trailing "h" (or "H") in which case they are inter-
       preted as hexadecimal.  Suffix multipliers  are  permitted  on  decimal
       values (e.g. '--num=1m').

       When the '--lba=' option is given then the '--num=' option must also be
       given. If one has a comma separated list as its argument then the other
       must  have  the  same number of elements in its list. The arguments can
       use a single space as a separator but need to be in quotes  or  escaped
       to not be misinterpreted by the shell.

       With  the '--in=FILE' option an even number of values must be found and
       are interpreted as pairs: the first value in each pair  is  a  starting
       LBA  and  the second value is the number to unmap from that LBA. Every-
       thing from and including a "#" on a line is ignored as are blank lines.
       Values  may  be  comma,  space  and tab separated or appear on separate
       lines. Each line should not exceed 1023 bytes in length.

       Since a lot of data can be lost with this utility, a 15 second "cooling
       off"  period  is  given before any UNMAP commands are sent. During this
       period the user is reminded what will happen, and to which  device,  so
       they  can  use  control-C  (or  some other technique) to terminate this
       utility before any unmapping takes place. This period can  be  bypassed
       with the --force option.

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

       -A, --all=ST,RN[,LA]
              where  ST  is the starting LBA, RN is the repeat number which is
              the maximum number of blocks in each SCSI UNMAP command, and LA,
              if given, is the last LBA to unmap. If LA is not given, then the
              last LBA on the DEVICE is used. That is  obtained  by  the  SCSI
              READ CAPACITY command.

       -a, --anchor
              sets the 'Anchor' bit in the command (introduced in sbc3r22).

       -d, --dry-run
              perform all the preparation, including opening DEVICE plus send-
              ing a 'standard' SCSI INQUIRY command  (and  optionally  a  READ
              CAPACITY), but exit before performing any SCSI UNMAP commands.

       -f, --force
              bypass the 15 second warning period that occurs before any UNMAP
              commands are sent.

       -g, --grpnum=GN
              sets the 'Group number' field to GN.  Defaults  to  a  value  of
              zero.  GN should be a value between 0 and 63.

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

       -I, --in=FILE
              where  FILE is a file name containing pairs of values. The first
              member of each pair is a starting LBA and the second  member  of
              the  pair  is  the  number  of  logical blocks to unmap from and
              including that starting LBA. Values are interpreted  as  decimal
              unless  indicated  otherwise. This option cannot be present with
              the '--lba=' option.

       -l, --lba=LBA,LBA...
              where LBA,LBA... is a string of comma (or space) separated  val-
              ues  that  are  interpreted as starting logical block addresses.
              Each number is interpreted as decimal unless prefixed by '0x' or
              '0X'  (or  it  has a trailing 'h' or 'H'). An argument that con-
              tains any space separators needs  to  be  quoted  (or  otherwise
              escaped).  When  this  option  is given then the '--num=' option
              must also be given and they must contain the same number of ele-
              ments in their arguments.

       -n, --num=NUM,NUM...
              where  NUM,NUM... is a string of comma (or space) separated val-
              ues that are interpreted as a number of logical blocks to unmap.
              Each number is interpreted as decimal unless prefixed by '0x' or
              '0X' (or it has a trailing 'h' or 'H'). Note that  0  blocks  is
              acceptable. An argument that contains any space separators needs
              to be quoted (or otherwise escaped).  When this option is  given
              then  the  '--lba=' option must also be given and they must con-
              tain the same number of elements in their arguments.

       -t, --timeout=TO
              where TO is a timeout value (in seconds) for the UNMAP  command.
              The default value is 60 seconds.

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

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


ATTRIBUTES
       See attributes(7) for descriptions of the following attributes:


       +---------------+--------------------------+
       |ATTRIBUTE TYPE |     ATTRIBUTE VALUE      |
       +---------------+--------------------------+
       |Availability   | system/storage/sg3_utils |
       +---------------+--------------------------+
       |Stability      | Pass-through uncommitted |
       +---------------+--------------------------+

NOTES
       Some  limits: an LBA can be up to 64 bits, a NUM up to 32 bits (imposed
       by structure of UNMAP SCSI command parameter data). The NUM is  further
       constrained  by  the  MAXIMUM UNMAP LBA COUNT field in the BLOCK LIMITS
       VPD page (0xb0). The maximum number of LBA,NUM pairs is limited to  128
       by  this  utility  and  may be further constrained by the MAXIMUM UNMAP
       BLOCK DESCRIPTOR COUNT field in the BLOCK LIMITS VPD page.

       Since it is unclear how long the UNMAP command will take to  execute  a
       '--timeout=" option has been provided. The default timeout period is 60
       seconds. If all the logical blocks on a  logical  unit  (e.g.   a  disk
       drive)  are  to  be unmapped then the FORMAT UNIT SCSI command (see the
       sg_format utility) may be considered as an alternative.

       Support for logical block provisioning is indicated by the LBPME bit in
       the response to the SCSI READ CAPACITY (16) command (see the sg_readcap
       utility).

       In SBC-3 revision 25 the LBPU and ANC_SUP bits where added to the Logi-
       cal Block Provisioning VPD page. When LBPU is set it indicates that the
       device supports the UNMAP command. When the ANC_SUP bit is set it indi-
       cates the device supports anchored LBAs.

       The  SCSI  UNMAP command does the "right thing" with respect to command
       queueing. However its ATA counterpart: the DATA SET MANAGEMENT  command
       with the "Trim" bit set does not interact well with SATA queueing known
       as NCQ.  To address this problem T13  have  introduced  a  new  command
       called SFQ DATA SET MANAGEMENT which also has a Trim bit.

       Source  code  for open source software components in Oracle Solaris can
       be found at https://www.oracle.com/downloads/opensource/solaris-source-
       code-downloads.html.

       This     software     was    built    from    source    available    at
       https://github.com/oracle/solaris-userland.   The  original   community
       source was downloaded from  http://sg.danny.cz/sg/p/sg3_utils-1.46.tgz.

       Further information about this software can be found on the open source
       community website at http://sg.danny.cz/sg/sg3_utils.html.

EXAMPLES
       In  the  examples  directory  of  the  sg3_utils  package  there  is  a
       sg_unmap_example.txt file that shows the format that the '--in=' option
       accepts.

       To unmap all blocks from and including LBA 0x2000 to  the  end  of  the
       device  (e.g.  disk  or  SSD)  with  each SCSI UNMAP command given 1024
       blocks to unmap:

         sg_unmap --all=0x2000,1k /dev/sg2

       Add '--force' to bypass the 15 seconds of  warnings.  So  '--force'  is
       appropriate for batch files.

EXIT STATUS
       The  exit  status of sg_unmap 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) 2009-2018 Douglas Gilbert
       This software is distributed under a FreeBSD license. There is NO  war-
       ranty;  not  even  for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR-
       POSE.

SEE ALSO
       sg_format,sg_get_lba_status,sg_readcap,sg_vpd,sg_write_same(sg3_utils)




sg3_utils-1.43                    March 2018                       SG_UNMAP(8)