C141-E078-02EN 1 - 3
(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.
