Fujitsu MHC2040AT, MHC2032AT, MHD2021AT, MHD2032AT Read-ahead data New read-ahead data Hit data

6.5 Read-Ahead Cache

b.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.

1)In the case that the contents of buffer is as follows at receiving a read command;

HAP (Continued from the previous read request data)

Read-ahead data Hit data

DAP

Last LBA Start LBA

2)The disk drive starts the read-ahead operation to the empty area that becomes vacant by data transfer at the same time as the disk drive starts transferring hit data.

HAP

Read-ahead data New read-ahead data Hit data

DAP

3)After completion of data transfer of hit data, the disk drive performs the read- ahead operation for the data area of which the disk drive transferred hit data.

HAP

Read-ahead data

DAP

C141-E050-02EN 6-19