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C141-E045-02EN6 - 18
4) The disk drive performs the read-ahead operation for all area of segment with
overwriting the requested data. Finally, the cache data in the buffer is as follows.
Start LBALast LBA
DAP
HAP
Read-ahead data
b. Sequential hit
When the previously executed read command is the sequential command and the last
sector address of the previous read command is sequential to the lead sector address of the
received read command, the disk drive transfers the hit data in the buffer to the host
system.
The disk drive performs the read-ahead operation of the new continuous data to the empty
area that becomes vacant by data transfer at the same time as the disk drive starts
transferring data to the host system.
1) In the case that the contents of buffer is as follows at receiving a read command;
Start LBALast LBA
DAP
HAP (Completion of transferring requested data)
Hit dataRead-ahead data
2) The disk drive starts the read-ahead operation to the empty area that becomes vacant
by data transfer at the same time as the disk drive starts transferring hit data.
DAP
HAP
Hit dataNew read-ahead dataRead-ahead data