Fujitsu MHN2100AT - Mobile 10 GB Hard Drive Product Manual page 218

Operations
2) The disk drive transfers the requested data that is already read to the host
system with reading the requested data.
HAP
Requested data
3) After completion of the reading and transferring the requested data to the host
system, the disk drive performs the read-ahead operation continuously.
Requested data
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.
b.
6-16
Mis-hit data
DAP
HAP (Completion of transferring requested data)
HAP
Read-ahead data
DAP
Last LBA Start LBA
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.
Empty area
Read-ahead data Empty area
DAP
C141-E120-02EN