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authorWeiping Zhang <zhangweiping@didichuxing.com>2018-02-26 22:08:28 +0800
committerMartin K. Petersen <martin.petersen@oracle.com>2018-03-01 21:26:54 -0500
commit18d595bf9de99a0f092d8522da42df8b09ef5c2f (patch)
tree0b23079c90a6f9ba5c3676ede8b8f3530912dafb /Documentation/scsi
parent29e79e0fa9b86535c2f1442d080c8cb5dec8606b (diff)
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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: Weiping Zhang <zhangweiping@didichuxing.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
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diff --git a/Documentation/scsi/sd-parameters.txt b/Documentation/scsi/sd-parameters.txt
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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