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Commit 18d595bf authored by Weiping Zhang's avatar Weiping Zhang Committed by Martin K. Petersen
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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: default avatarWeiping Zhang <zhangweiping@didichuxing.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 29e79e0f
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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