Fujitsu MHV2040AH 用户手册
Operations
6-12
C141-E217
6.4 Read-ahead Cache
Read-ahead Cache is the function for automatically reading data blocks upon
completion of the read command in order to read data from disk media and save
data block on a data buffer.
completion of the read command in order to read data from disk media and save
data block on a data buffer.
If a subsequent command requests reading of the read-ahead data, data on the data
buffer can be transferred without accessing the disk media. As the result, faster
data access becomes possible for the host.
buffer can be transferred without accessing the disk media. As the result, faster
data access becomes possible for the host.
6.4.1 DATA buffer structure
This device contains a data buffer. This buffer is divided into two areas: one area
is used for MPU work, and the other is used as a read cache for another command.
(See Figure 6.7)
is used for MPU work, and the other is used as a read cache for another command.
(See Figure 6.7)
a) 8MB buffer (8,388,608 bytes)
For MPU work
For R/W command
8,388,608 bytes
557,056
bytes
7,831,552
bytes
Figure 6.7 Data buffer structure
The read-ahead operation is done by the following commands.
•
READ SECTOR(S) (EXT)
•
READ MULTIPLE (EXT)
•
READ DMA (EXT)
•
READ SECTOR(S) EXT
•
READ DMA EXT
•
READ MULTIPLE EXT