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1.1 Standard Features
C141-E163 1-3
(6) Programmable multi-segment data buffer
The data buffer is 8M bytes. Data is transferred between Fibre Channel Loop and disk media
through this data buffer. 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 Loop regardless of actual data transfer rate of the disk drive.
(7) 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.
You should ensure that the cached data is surely flushed to the disc media
before you turn off the drive's power.
To ensure it, you should issue either the SYNCHRONIZE CACHE
command or the STOP UNIT command, and then confirm that the
command is surely terminated with the GOOD STATUS.
(8) Command queuing feature
The IDD can queue maximum 128 commands, and optimizes the issuing order of queued commands
by the reordering function. This feature realizes the high speed processing.
(9) 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.
(10) Enclosure service function
The IDD supports the enclosure service interface (ESI), which complies with SFF-8067. The ESI
interface enables use of the SCSI-3 enclosure service command set (SES) so that the functions that
specify and read enclosure service information can be used.
(11) 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.