linux-arkmicro/linux/Documentation/scsi/sd-parameters.txt

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