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1.1 Standard Features
C141-E198 1-3
(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.
The Write Cache feature is supported. When this feature is enabled, the status report is issued
without waiting for completion of write processing to disk media, thereby enabling high speed write
processing.
When Write Cache is enabled, 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 with specifying “0” to the
Immediate bit, 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.