Fujitsu MHY2040BS Manuale Utente

 

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. 

(1)  Command that are targets of caching 

The Commands that are targets of caching are as follows: 

WRITE SECTOR(S) (EXT) 

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WRITE MULTIPLE (EXT) (FUA) 

WRITE DMA (EXT) (FUA) 

WRITE FP DMA QUEUED 

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, write processing is repeated up to as 
many times as specified for retry processing. If retry fails for a sector because the 
retry limit is reached, automatic alternate sector processing is executed for the 
sector. If the automatic alternate sector processing fails, the data in the sector for 
which automatic alternate sector processing failed is invalidated without being 
guaranteed. 

Moreover, when the command (clause 6.4.2(3)) is accepted and HOST CRC Error 
is generated, the cashing data is invalidated. 

<Exception> 

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If a COMRESET, a software 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, and sectors accepted before interruption 
occurred is written in the medium. 

6-20 

C141-E269