Fujitsu MHY2040BS, MHY2160BS, MHY2200BS, MHY2120BS, MHY2080BS, MHY2060BS, MHY2100BS Sequential hit

6.4 Read-ahead Cache

6.4.3.2 Sequential hit

When the read command that is targeted at a sequential address is received after execution of the read commands is completed, the read command transmits the Read requested data to the host system continuing read-ahead without newly allocating the buffer for read.

1)When the sequential read command is received, HAP is set in the sequential address of the last read command, and DAP is set at a present read position as it is.

	HAP (host address pointer)
Cache valid data		Read requested data		Free space
		Read-ahead da	ta

DAP (disk address pointer)

2)During reading of read requested data, the request data that has already been read is sent to the host system.

HAP (host address pointer)

Cache valid data Read requested data Free space

DAP (disk address pointer)

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.

HAP (host address pointer)

Cache valid data	Read requested data	Read-ahead	Free
		data	space

DAP (disk address pointer)

4) The following cache valid data is for the read command that is executed next:

Cache valid data

LAST LBA START LBA

C141-E269 6-17