73 lines
3.3 KiB
Groff
73 lines
3.3 KiB
Groff
.TH SG_BG_CTL "8" "May 2016" "sg3_utils\-1.43" SG3_UTILS
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.SH NAME
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sg_bg_ctl \- send SCSI BACKGROUND CONTROL command
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.SH SYNOPSIS
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.B sg_bg_ctl
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[\fI\-\-ctl=CTL\fR] [\fI\-\-help\fR] [\fI\-\-time=TN\fR] [\fI\-\-verbose\fR]
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[\fI\-\-version\fR] \fIDEVICE\fR
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.SH DESCRIPTION
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.\" Add any additional description here
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.PP
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Sends a SCSI BACKGROUND CONTROL command to the \fIDEVICE\fR. This command
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was first found in the SBC\-4 draft standard revision 8 (sbc4r08.pdf). It can
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be used to start and stop 'advanced background operations' on the
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\fIDEVICE\fR. Only resource or thin provisioned devices (logical units which
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are typically (solid state) disks) support this command. Those advanced
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background operations often include garbage collection type operations which
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may degrade the disk's performance while they are being performed.
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.SH OPTIONS
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Arguments to long options are mandatory for short options as well.
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.TP
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\fB\-c\fR, \fB\-\-ctl\fR=\fICTL\fR
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\fICTL\fR is the value placed in the BO_CTL field of the BACKGROUND CONTROL
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command (cdb). It is a two bit field so has 4 variants: 0 does not change
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the host initiated advanced background operations; 1 starts these operations;
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2 stops these operations and 3 is reserved. The default value is 0.
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.TP
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\fB\-h\fR, \fB\-\-help\fR
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output the usage message then exit.
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.TP
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\fB\-t\fR, \fB\-\-time\fR=\fITN\fR
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\fITN\fR is a maximum time (with a unit of 100 ms or 1/10 second) that
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advanced background operations can occur. This value is ignored if the
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\fICTL\fR argument is other than 1. The default value is 0 which means there
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is no maximum time limit. Only values 0 to 255 (which is 25.5 seconds) can
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be given. This value is place in the BO_TIME field of the BACKGROUND CONTROL
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command.
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.TP
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\fB\-v\fR, \fB\-\-verbose\fR
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increase the level of verbosity, (i.e. debug output).
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.TP
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\fB\-V\fR, \fB\-\-version\fR
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print the version string and then exit.
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.SH NOTES
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According to T10, support for 'background control operations' is indicated by
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the BOCS bit being set in the Block device characteristics VPD page [0xb1].
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The setting of the BOCS bit can be checked with the sg_vpd and sdparm
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utilities (and it is read only). There is a Background operations control
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mode page [0xa, 0x6] with a BO_MODE field for modifying the action of this
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operation. The BO_MODE field can be accessed and possibly modified with the
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sdparm utility. The BO_STATUS field can be found in the Background operation
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log page [0x15, 0x2] and that can be viewed with the sg_logs utility.
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.PP
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The current draft describing this area is SBC\-4 revision 10 (sbc4r10.pdf)
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in clause 4.33 . That contains the following example of a background
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operation: "Advanced background operation may include NAND block erase
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operations, media read operations, and media write operations (e.g.,
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garbage collection), which may impact response time for normal read requests
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or write requests from the application client."
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.SH EXIT STATUS
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The exit status of sg_bg_ctl is 0 when it is successful. Otherwise see
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the sg3_utils(8) man page.
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.SH AUTHORS
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Written by Douglas Gilbert.
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.SH "REPORTING BUGS"
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Report bugs to <dgilbert at interlog dot com>.
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.SH COPYRIGHT
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Copyright \(co 2016 Douglas Gilbert
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.br
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This software is distributed under a BSD\-2\-Clause license. There is NO
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warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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.SH "SEE ALSO"
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.B sg_vpd,sg_logs(sg3_utils); sdparm(sdparm)
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