Fujitsu MHY2200BS Product/Maintenance Manual page 285

6.4.3.4 Partial hit
In this situation, a part of read requested data including the top sector is stored in
the data buffer. A transfer of the read requested data starts from the address where
the data that is hit is stored until the top sector of the read requested data.
Remaining part of insufficient data is read then.
An example is a case where a partial hit occurs in cache data, as shown below.
START LBA
1) HAP is set at the address where partial hit data is stored, and Transfer is
started.
2) DAP and HAP are set at the head of Buffer newly allocated, and insufficient
data is read.
HAP (host address pointer)
DAP (disk address pointer)
3) When reading the read requested data ends and the transmission of the read
requested data to the host system ends, the read-ahead operation continues
until a certain amount of data is stored.
The method of storing the read-ahead data at Partial hit is the same as the
Miss hit.
C141-E269
Cache valid data
HAP (host address pointer)
Cache valid data
Read segment
Cache valid data
LAST LBA START LBA
6.4 Read-ahead Cache
LAST LBA
Partial hit data
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