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13.11 Write cache function
Write cache is a performance enhancement whereby the device reports the completion of the write
command—Write Sectors, Write Multiple, and Write DMA—to the host as soon as the device has
received all of the data into its buffer. The device assumes the responsibility of subsequently writing the
data onto the disk.
O
While writing data after completed acknowledgment of a write command, soft reset or hard reset
does not affect its operation. However power off terminates the writing operation immediately and
unwritten data is lost.
O
The Soft reset, Standby (Immediate) command, and Flush Cache commands during the writing of the
cached data are executed after the completion of writing to media. So the host system can confirm
the completion of write cache operation by issuing a Soft reset, Standby (Immediate) command, or
Flush Cache command and then confirming its completion. It is recommended that the host system
checks the completion of the write cache operation by issuing Soft reset, the Standby (Immediate)
command, or the Flush Cache command to the device before power off.
O
The retry bit of Write Sectors is ignored when write cache is enabled.
13.12 Reassign Function
Reassign Function is used with read commands and write commands. The sectors of data for
reassignment are prepared as the spare data sector.
This reassignment information is registered internally and the information is available right after
completing the reassign function. Also the information is used on the next power on reset or hard reset.
If the number of the spare sector reaches 0 sector, the reassign function will be disabled automatically.
The spare sectors for reassignment are located at the end of device. As a result of reassignment the
physical location of logically sequenced sectors will be dispersed.
13.13 Auto Reassign Function
The sectors which show some errors may be reallocated automatically when specific conditions are met.
The spare sectors for reallocation are located at the end of drive. The conditions for auto-reallocation are
described in the following paragraphs.
13.13.1 Nonrecovered write errors
When a write operation cannot be completed after the Error Recovery Procedure (ERP) is fully carried
out, the sector(s) are reallocated to the spare location. An error is reported to the host system only when
the write cache is disabled and the auto reallocation has failed.
If the write cache function is ENABLED—and when the number of available spare sectors reaches
0 sectors—both the auto reassign function and the write cache function are disabled automatically.
13.13.2 Nonrecovered read errors
When a read operation is failed after defined ERP is fully carried out, a hard error is reported to the host
system. This location is registered internally as a candidate for the reallocation. When a registered
location is specified as a target of a write operation, a sequence of media verification is performed
automatically. When the result of this verification meets the criteria, this sector is reallocated.
Deskstar 60 GXP Hard disk drive specification
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