Fujitsu MHT2020AT, Product Manual

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6.4 Read-ahead Cache
C141-E192-01EN 6-17
4) The following cache valid data is for the read command that is executed next:
Cache valid data
START LBA LAST LBA
6.4.3.3 Full hit
In this situation, all read requested data is stored in the data buffer. Transfer of
the read requested data is started from the location where hit data is stored. For
data that is a target of caching and remains before a full hit, the data is retained
when execution of the command is completed. This is done so that a new read-
ahead operation is not performed. If the full hit command is received during the
read-ahead operation, a transfer of the read requested data starts while the read-
ahead operation is in progress.
1) An example is the state shown below where the previous read command is
executing sequential reading. First, HAP is set at the location where hit data
is stored.
HAP (It is reset to the hit data location for transfers.)
HAP end location of the previous read command
DAP end location of the previous read command
Cache data Full hit data Cache data
HAP
DAP
2) The read requested data is transferred, and a new read-ahead operation is not
performed.
(stop)
HAP
Cache data Full hit data Cache data