Conner CFP4207 Series Product Manual - Write Caching

Chapter 3

Drive Operations

Page 26

Filepro CFP4207 Series

Write Caching

Write Caching allows multiple write commands operating on sequential blocks to

be written to the medium without losing a motor revolution between commands.

Write caching is enabled by setting the WCE bit in MODE SELECT page 8 to

one.

The drive will send good status and command complete following the data out

phase of a cached write command.  The drive will cache writes when the

following conditions are met:

•

Two or more write commands (Op Code 0A

H

 or 2A

H

) execute consecutively

without an intervening command.

•

The write commands address consecutive logical block ranges.

•

At least one logical block of data has been received in the buffer from the

second write command in time to allow the medium to be written before an

additional spindle revolution would be required.

•

Both writes are from the same initiator.

•

Neither write is a linked command.

If the drive encounters an error during a cached write operation, the drive will

respond by:

If AWRE (MODE SELECT page 01

H

) is 0:  the drive will report a CHECK

CONDITION on the next command and the response from a REQUEST SENSE

will be a deferred error.  (Asynchronous event notification is not supported by

this drive.)  Refer to the Eleventh Generation SCSI Interface Manual for

additional details.

If AWRE (MODE SELECT page 01

H

) is set to 1:  the drive will attempt to

dynamically reassign the block of data and complete the operation.  If the

reassignment fails, the drive will continue to reassign the block until all the

space in the grown defect list is filled (147 sectors, maximum).