Fujitsu MCM3130AP, MCM3064AP manual Features, Read-ahead cache feature

1.1 Features

(4) Read-ahead cache feature

The read-ahead cache feature enables high-speed sequential data access as follows:

After executing a command to read data from the disk, the drive automatically reads the next data block and stores it in the data buffer (pre-reading). If the next command requests this data, the drive can transfer data from the buffer without accessing the disk again.

(5) Write cache feature

When the host system issues the write command to the optical disk drive, this drive would report completion of the command after completion of the write and verify operations if the write cache feature were not used. If the write cache feature is used, this drive reports completion of the command when data transfer to buffer is completed, without waiting for completion of the write and verify operations. This drive performs the write and verify operations asynchronously with the interface operation. Therefore, enabling the write cache reduces the apparent write command processing time recognized by the host system and improves the I/O performance of the host system.

Enable or disable the write cache feature using the MODE SELECT command.

While the write cache feature is enabled, a write error is reported in the completion status of another command that is subsequent to the concerned write command. Note that, if the host performs only retry of an error-reporting command, data in the block in which the error has occurred is not correctly written.

(6) Defective block slipping

While initializing a disk, the optical disk drive slips defective data blocks to reallocate logical data blocks so they are physically continuous. This enables high-speed continuous data block processing without rotational delay due to defective data blocks.

C156-E227-01EN 1-5