scsi: sd: Documentation: add sd-parameters.txt

Add a file for documenting SCSI sd module parameters and describe the
cache_type setting.

[mkp: tweaked text a bit]

Signed-off-by: Weiping Zhang <zhangweiping@didichuxing.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Weiping Zhang 2018-02-26 22:08:28 +08:00 committed by Martin K. Petersen
parent 29e79e0fa9
commit 18d595bf9d

View File

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Linux SCSI Disk Driver (sd) Parameters
======================================
cache_type (RW)
---------------
Enable/disable drive write & read cache.
cache_type string | WCE RCD | Write cache | Read cache
----------------------------+---------+-------------+------------
write through | 0 0 | off | on
none | 0 1 | off | off
write back | 1 0 | on | on
write back, no read (daft) | 1 1 | on | off
To set cache type to "write back" and save this setting to the drive:
# echo "write back" > cache_type
To modify the caching mode without making the change persistent, prepend
"temporary " to the cache type string. E.g.:
# echo "temporary write back" > cache_type