IBM IC35L036UWDY10 Hard Drive Specifications - Page 224

Segmented Caching, 10 Reselection Timeout, 11 Single Initiator Selection, 12 Non-arbitrating systems

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11.9 Segmented Caching Segmented Caching divides the data buffer into several buffer segments. Size and number of segments are determined by Number of Cache Segments, Cache Segment Size, SIZE and LBCSS (Mode Page 8). Number of Segments can be 1 through 255. (256 segments can be used by specifying segment size.) The Read Ahead is a function that read data that the initiator has not yet requested to the buffer segment. This function is intended to improve performance for an initiator that frequently accesses sequential data with successive SCSI read commands. The Read Ahead works for READ (6), READ (10), VERIFY, the verify portion of WRITE AND VERITY command when RCD (Mode Page 8) is set to zero. Even if an error occurs during the Read ahead, the error will not be reported to the initiator. The data read before the error occurred will be stored as valid data by the Read Ahead function. If SCSI Bus Reset or TARGET RESET message is received, all contents of segmented buffer is flushed. 11.10 Reselection Timeout If a RESELECTION fails, the drive retries up to 16 times. Between each retry, the drive waits 200 µs. When all the retries fail, the command is ignored. 11.11 Single Initiator Selection For single initiator systems it is not an error to have only the drive ID bit present during SELECTION. Disconnection is not allowed for Single Initiator Selection with only one ID bit present during SELECTION. The initiator must not send an IDENTIFY message with the disconnect permission (bit 6) on. 11.12 Non-arbitrating systems The drive cannot detect whether other SCSI devices on the SCSI bus use arbitration prior to SELECTION. As a consequence the drive allows disconnect permission to be enabled by the IDENTIFY message independent of the initiator's use of arbitration prior to SELECTION. A non-arbitrating initiator must ensure that disconnect permission in the IDENTIFY message is disabled (bit 6=0) for proper operation. 11.13 Selection without ATN If the drive is selected without ATN signal active, no IDENTIFY message is received from the Initiator. In this case the LUN is identified as 0 and disconnect permission is disabled. The drive does not perform any phase retries. The drive still responds to a subsequent attention condition. The drive also knows the use of linked commands if selected without ATN. Phase retries may be allowed if a subsequent IDENTIFY message is received. Ultrastar 146Z10 hard disk drive specifications 208

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11.9 Segmented Caching
Segmented Caching divides the data buffer into several buffer segments. Size and number of segments
are determined by Number of Cache Segments, Cache Segment Size, SIZE and LBCSS (Mode Page 8).
Number of Segments can be 1 through 255. (256 segments can be used by specifying segment size.)
The Read Ahead is a function that read data that the initiator has not yet requested to the buffer segment.
This function is intended to improve performance for an initiator that frequently accesses sequential data
with successive SCSI read commands. The Read Ahead works for READ (6), READ (10), VERIFY, the
verify portion of WRITE AND VERITY command when RCD (Mode Page 8) is set to zero.
Even if an error occurs during the Read ahead, the error will not be reported to the initiator. The data read
before the error occurred will be stored as valid data by the Read Ahead function.
If SCSI Bus Reset or TARGET RESET message is received, all contents of segmented buffer is flushed.
11.10 Reselection Timeout
If a RESELECTION fails, the drive retries up to 16 times. Between each retry, the drive waits 200
ยต
s.
When all the retries fail, the command is ignored.
11.11 Single Initiator Selection
For single initiator systems it is not an error to have only the drive ID bit present during SELECTION.
Dis-
connection is not allowed for Single Initiator Selection with only one ID bit present during SELECTION.
The initiator must not send an IDENTIFY message with the disconnect permission (bit 6) on.
11.12 Non-arbitrating systems
The drive cannot detect whether other SCSI devices on the SCSI bus use arbitration prior to SELECTION.
As a consequence the drive allows disconnect permission to be enabled by the IDENTIFY message inde-
pendent of the initiator's use of arbitration prior to SELECTION. A non-arbitrating initiator must ensure that
disconnect permission in the IDENTIFY message is disabled (bit 6=0) for proper operation.
11.13 Selection without ATN
If the drive is selected without ATN signal active, no IDENTIFY message is received from the Initiator. In
this case the LUN is identified as 0 and disconnect permission is disabled. The drive does not perform any
phase retries. The drive still responds to a subsequent attention condition.
The drive also knows the use
of linked commands if selected without ATN.
Phase retries may be allowed if a subsequent IDENTIFY message is received.
Ultrastar 146Z10 hard disk drive specifications
208