Fujitsu MHW2100BS, MHW2080BS, MHW2120BS, MHW2040BS, MHW2060BS manual Partial hit

6.4 Read-ahead Cache

6.4.3.4 Partial hit

In this situation, a part of read requested data including the top sector is stored in the data buffer. A transfer of the read requested data starts from the address where the data that is hit is stored until the top sector of the read requested data.

Remaining part of insufficient data is read then.

An example is a case where a partial hit occurs in cache data, as shown below.

Cache valid data

START LBA
	LAST LBA

1)HAP is set at the address where partial hit data is stored, and Transfer is started.

HAP (host address pointer)

Cache valid data

Partial hit data

2)DAP and HAP are set at the head of Buffer newly allocated, and insufficient data is read.

HAP (host address pointer)

Read segment

DAP (disk address pointer)

3)When reading the read requested data ends and the transmission of the read requested data to the host system ends, the read-ahead operation continues until a certain amount of data is stored.

The method of storing the read-ahead data at Partial hit is the same as the Miss hit.

Cache valid data

LAST LBA START LBA

C141-E249 6-19