Fujitsu MAG3182FC manual 7 4MB programmable multi-segment data buffer, Read-ahead cache feature

(7)4MB programmable multi-segment data buffer

Data is transferred between fibre-channel loop and disk media through the embedded 4MB data buffer in the IDD. This buffer can be divided into maximum 32 areas. This feature provides the suitable usage environment for users.

Since the initiator can control the disconnect/reconnect timing on the fibre-channel loop by specifying the condition of stored data to the data buffer or empty condition of the data buffer, the initiator can perform the effective input/output operations with utilizing high data transfer capability of the fibre-channel regardless of actual data transfer rate of the disk drive.

(8)Read-ahead cache feature

After executing the READ command, the IDD reads automatically and stores (prefetches) the subsequent data blocks into the data buffer (Read-ahead caching).

The high speed sequential data access can be achieved by transferring the data from the data buffer without reaccessing the disk in case the subsequent command requests the prefetched data blocks.

(9)Command queuing feature

The IDD can queue maximum 63 commands, and optimizes the issuing order of queued commands by the reordering function. This feature realizes the high speed processing.

(10)Reserve and release functions

The IDD can be accessed exclusively in the multi-host or multi-initiator environment by using the reserve and release functions.

(11)Enclosure service function

The IDD supports an enclosure service interface (ESI) compliant with the SFF-8067. This interface provides the function of setting/readin enclosure service information using the SCSI-3 enclosure service command set (SES).

(12)Error recovery

The IDD can try to recover from errors in fibre-channel loop or the disk drive using its powerful retry processing. If a recoverable data check occurs, error-free data can be transferred to the initiator after being corrected in the data buffer. The initiator software is released from the complicated error recover processing by these error recovery functions of the IDD.

(13)Automatic alternate block reassignment

If a defective data block is detected during read, the IDD can automatically reassign its alternate data block.

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