Write Cache; Caching Operation - Fujitsu MHR2010AT Product Manual

6.5 Write Cache

Write Cache is the function for reducing the command processing time by
separating command control to disk media from write control to disk media.
When Write Cache is permitted, the write command can be keep receiving as long
as the space available for data transfers remains free on the data buffer. Because
of this function, command processing appears to be completed swiftly from the
viewpoint of the host. It improves system throughput.

6.5.1 Caching operation

(1) Commands that are targets of caching
The commands that are targets of caching are as follows:
WRITE SECTOR (S)
WRITE MULTIPLE
WRITE DMA
WRITE SECTOR (S) EXT
WRITE MULTIPLE EXT
WRITE DMA EXT
However, the caching operation is not performed when the caching function is
prohibited by the SET FEATURES command.
(2) Invalidation of cached data
If an error occurs during writing onto media, the sector that causes the error is
skipped and its data is not assured and becomes invalidated. If data remains in
sectors after the sectors that caused the error, writing data continues from the next
sector.
For the sector that caused the error, write processing is repeated as many times as
specified for retry processing. In such cases, the sector that caused the error is
skipped during write processing repeated.
<Exception>
If a reset or command is received while a transfer of one sector of data is in
progress, data is not written in the sector of the media where the interruption
occurred.
C141-E145-02EN
6.5 Write Cache
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