diff options
Diffstat (limited to 'doc/sg_unmap.8')
| -rw-r--r-- | doc/sg_unmap.8 | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/doc/sg_unmap.8 b/doc/sg_unmap.8 index 7eb0588c..5e8e5817 100644 --- a/doc/sg_unmap.8 +++ b/doc/sg_unmap.8 @@ -1,4 +1,4 @@ -.TH SG_UNMAP "8" "January 2014" "sg3_utils\-1.38" SG3_UTILS +.TH SG_UNMAP "8" "April 2014" "sg3_utils\-1.39" SG3_UTILS .SH NAME sg_unmap \- send SCSI UNMAP command (known as 'trim' in ATA specs) .SH SYNOPSIS @@ -22,7 +22,8 @@ and the corresponding number(s) to unmap to the '\-\-num=' option. The other way is by putting start LBA and number to unmap pairs in a file whose name is given to the '\-\-in=' 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 interpreted as hexadecimal. +case they are interpreted as hexadecimal. Suffix multipliers are permitted +on decimal values (e.g. '\-\-num=1m'). .PP 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 @@ -105,6 +106,12 @@ In SBC\-3 revision 25 the LBPU and ANC_SUP bits where added to the Logical 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 indicates the device supports anchored LBAs. +.PP +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. .SH 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=' |