Fujitsu MAN3184 User Manual
C141-E124-01EN
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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.
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.
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.