NAME

       sg_bg_ctl - send SCSI BACKGROUND CONTROL command

SYNOPSIS

       sg_bg_ctl [--ctl=CTL] [--help] [--time=TN] [--verbose] [--version] DEVICE

DESCRIPTION

       Sends a SCSI BACKGROUND CONTROL command to the DEVICE. This command was first found in the
       SBC-4 draft standard revision 8 (sbc4r08.pdf). It can be used to start and stop  'advanced
       background  operations'  on the DEVICE. Only resource or thin provisioned devices (logical
       units which are typically (solid  state)  disks)  support  this  command.  Those  advanced
       background  operations  often include garbage collection type operations which may degrade
       the disk's performance while they are being performed.

OPTIONS

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

       -c, --ctl=CTL
              CTL is the value placed in the BO_CTL  field  of  the  BACKGROUND  CONTROL  command
              (cdb).  It  is  a  two  bit  field  so  has  4 variants: 0 does not change the host
              initiated advanced background operations; 1 starts these operations; 2 stops  these
              operations and 3 is reserved. The default value is 0.

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

       -t, --time=TN
              TN  is  a  maximum  time  (with  a  unit  of  100  ms or 1/10 second) that advanced
              background operations can occur. This value is ignored if the CTL argument is other
              than  1.  The  default  value is 0 which means there is no maximum time limit. Only
              values 0 to 255 (which is 25.5 seconds) can be given. This value is  place  in  the
              BO_TIME field of the BACKGROUND CONTROL command.

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

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

NOTES

       According to T10, support for 'background control operations' is indicated by the BOCS bit
       being set in the Block device characteristics VPD page [0xb1].  The setting  of  the  BOCS
       bit  can be checked with the sg_vpd and sdparm utilities (and it is read only). There is a
       Background operations control mode page [0xa, 0x6] with a BO_MODE field for modifying  the
       action of this operation. The BO_MODE field can be accessed and possibly modified with the
       sdparm utility. The BO_STATUS field can be found in  the  Background  operation  log  page
       [0x15, 0x2] and that can be viewed with the sg_logs utility.

       The current draft describing this area is SBC-4 revision 10 (sbc4r10.pdf) in clause 4.33 .
       That contains the following  example  of  a  background  operation:  "Advanced  background
       operation  may include NAND block erase operations, media read operations, and media write
       operations (e.g., garbage collection), which may impact  response  time  for  normal  read
       requests or write requests from the application client."

EXIT STATUS

       The  exit  status  of sg_bg_ctl 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 © 2016 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_vpd,sg_logs(sg3_utils); sdparm(sdparm)