Fujitsu MHS2020AT, Product Manual

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Operations
6-16 C141-E171-03EN
4) The following cache valid data is for the read command that is executed next:
START LBA
(Logical block address)
Cache valid data
LAST LBA
6.4.3.2 Sequential reading
The read-ahead operation is performed for the read buffer when the read
command that is targeted at a sequential address is received after execution of the
read command is completed.
1. Sequential command immediately after non-sequential command
1) When the sequential read command is received, DAP and HAP are set in the
sequential address of the last read command, and read requested data is read.
Free space Hit error data
DAP
HAP
2) During reading of read requested data, the request data that has already been
read is sent to the host system.
Read requested data Hit error data Free space
HAP
DAP
3) When reading of read requested data is completed and transfer of the read
requested data to the host system is completed, the read-ahead operation
continues until a certain amount of data is stored.
Hit error data Read requested data
HAP
DAP
Read-ahead data Free space