1SG_BG_CTL(8) SG3_UTILS SG_BG_CTL(8)
2
3
4
6 sg_bg_ctl - send SCSI BACKGROUND CONTROL command
7
9 sg_bg_ctl [--ctl=CTL] [--help] [--time=TN] [--verbose] [--version]
10 DEVICE
11
13 Sends a SCSI BACKGROUND CONTROL command to the DEVICE. This command was
14 first found in the SBC-4 draft standard revision 8 (sbc4r08.pdf). It
15 can be used to start and stop 'advanced background operations' on the
16 DEVICE. Only resource or thin provisioned devices (logical units which
17 are typically (solid state) disks) support this command. Those advanced
18 background operations often include garbage collection type operations
19 which may degrade the disk's performance while they are being per‐
20 formed.
21
23 Arguments to long options are mandatory for short options as well.
24
25 -c, --ctl=CTL
26 CTL is the value placed in the BO_CTL field of the BACKGROUND
27 CONTROL command (cdb). It is a two bit field so has 4 variants:
28 0 does not change the host initiated advanced background opera‐
29 tions; 1 starts these operations; 2 stops these operations and 3
30 is reserved. The default value is 0.
31
32 -h, --help
33 output the usage message then exit.
34
35 -t, --time=TN
36 TN is a maximum time (with a unit of 100 ms or 1/10 second) that
37 advanced background operations can occur. This value is ignored
38 if the CTL argument is other than 1. The default value is 0
39 which means there is no maximum time limit. Only values 0 to 255
40 (which is 25.5 seconds) can be given. This value is place in the
41 BO_TIME field of the BACKGROUND CONTROL command.
42
43 -v, --verbose
44 increase the level of verbosity, (i.e. debug output).
45
46 -V, --version
47 print the version string and then exit.
48
50 According to T10, support for 'background control operations' is indi‐
51 cated by the BOCS bit being set in the Block device characteristics VPD
52 page [0xb1]. The setting of the BOCS bit can be checked with the
53 sg_vpd and sdparm utilities (and it is read only). There is a Back‐
54 ground operations control mode page [0xa, 0x6] with a BO_MODE field for
55 modifying the action of this operation. The BO_MODE field can be
56 accessed and possibly modified with the sdparm utility. The BO_STATUS
57 field can be found in the Background operation log page [0x15, 0x2] and
58 that can be viewed with the sg_logs utility.
59
60 The current draft describing this area is SBC-4 revision 10
61 (sbc4r10.pdf) in clause 4.33 . That contains the following example of a
62 background operation: "Advanced background operation may include NAND
63 block erase operations, media read operations, and media write opera‐
64 tions (e.g., garbage collection), which may impact response time for
65 normal read requests or write requests from the application client."
66
68 The exit status of sg_bg_ctl is 0 when it is successful. Otherwise see
69 the sg3_utils(8) man page.
70
72 Written by Douglas Gilbert.
73
75 Report bugs to <dgilbert at interlog dot com>.
76
78 Copyright © 2016 Douglas Gilbert
79 This software is distributed under a FreeBSD license. There is NO war‐
80 ranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PUR‐
81 POSE.
82
84 sg_vpd,sg_logs(sg3_utils); sdparm(sdparm)
85
86
87
88sg3_utils-1.43 May 2016 SG_BG_CTL(8)