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6.5 Read-Ahead Cache
C141-E050-02EN 6-17
2) Transfers the requested data that already read to the host system with reading
the requested data from the disk media.
Read-requested data
Stores the read-requested
data upto this point
Empty area
DAP
HAP
3) After reading the requested data and transferring the requested data to the host
system had been completed, the disk drive stops command execution without
performing the read-ahead operation.
Read-requested data
Empty area
DAP
(stopped)
(stopped)
HAP
4) Following shows the cache enabled data for next read command.
Cache enabled data
Empty area
6.5.3.2 Sequential read
When the disk drive receives the read command that targets the sequential address
to the previous read command, the disk drive starts the read-ahead operation.
a. Sequential command just after non-sequential command
When the previously executed read command is an non-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 assumes the received command is a sequential command and
performs the read-ahead operation after reading the requested data.
Start LBA
Last LBA