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SG_BG_CTL(8) SG3_UTILS SG_BG_CTL(8)
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 back-
ground 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 initi-
ated advanced background operations; 1 starts these operations; 2 stops these oper-
ations 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 back-
ground 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 opera-
tion may include NAND block erase operations, media read operations, and media write oper-
ations (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 (C) 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)
sg3_utils-1.43 May 2016 SG_BG_CTL(8)
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