1)In the case that the contents of the data buffer is as follows for example and the previous command is a sequential read command, the disk drive sets the HAP to the address of which the hit data is stored.

 

Last position at previous read command

HAP

HAP (set to hit position for data transfer)

Cache data

Full hit data

Cache data

DAP

Last position at previous read command

2) The disk drive transfers the requested data but does not perform the read-ahead operation.

HAP (stopped)

Cache data

Full hit data

Cache data

3)The cache data for next read command is as follows.

Cache data

Start LBA

Last LBA

(4)Partially hit

A part of requested data including a lead sector are stored in the data buffer. The disk drive starts the data transfer from the address of the hit data corresponding to the lead sector of the requested data, and reads remaining requested data from the disk media directly. The disk drive does not perform the read-ahead operation after data transfer.

Following is an example of partially hit to the cache data.

Cache data

Start LBA

Last LBA

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Fujitsu MPA3043AT, MPA3052AT, MPA3026AT, MPA3035AT, MPA3017AT manual HAP set to hit position for data transfer