Write Cache - Fujitsu MAP3147 Scsi Logical Interface Specifications

2.3

Write Cache

The IDD is equipped with a write cache function in order to reduce the INIT's command processing
time. If that operation is permitted by the MODE SELECT command (caching parameters: Page
code = 8, WCE bit), at the point when the IDD completes the transfer of all data specified in the
WRITE or WRITE EXTENDED command, it reports the GOOD status and terminates the
command.
Note:
If the write cache function is permitted, data transferred form the INIT by a WRITE or WRITE
EXTENDED command are written to the disk media after the GOOD status is reported, so when
an unrecoverable write error is detected in that write operation, sense data is generated. When
those sense data is being held, the IDD ordinarily responds to the command that is executed next
by a "CHECK" status (deferred error), notifying the INIT that sense data is being held.
However, ordinarily, it is troublesome for the INIT to retry when there is an unrecoverable error
in a write cache operation, so adequate caution should be exercised when using this function.
C141-E167
2.3 Write Cache
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