Seagate ST936701LC - Savvio 36.7 GB Hard Drive, Product Manual

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38 Savvio SCSI Product Manual, Rev. C
used when data integrity is not a concern and speed is of utmost importance. If the Recovery Time Limit or
retry count is reached during error recovery, the state of the RC bit is examined. If the RC bit is set, the drive
will transfer the unrecovered data with no error indication and continue to execute the remaining command. If
the RC bit is not set, the drive will stop data transfer with the last good LBA, and report a “Check Condition,
Unrecovered Read Error.”
[1] These values are subject to change.
Setting these retry counts to a value below the default setting could result in an increased unrecovered
error rate which may exceed the value given in this product manual. A setting of zero (0) will result in the
drive not performing error recovery.
For example, suppose the Read/Write Recovery page has the RC bit set to 0, read retry count set to 4,
and the recovery time limit field (Mode Sense page 01, bytes 10 and 11) set to FF FF hex (maximum). A
four LBA Read command is allowed to take up to 401
msec recovery time for each of the four LBAs in the
command. If the recovery time limit is set to 00 C8 hex (200 msec decimal) a four LBA read command is
allowed to take up to 200 msec for all error recovery within that command. The use of the Recovery Time
Limit field allows finer granularity on control of the time spent in error recovery. The recovery time limit
only starts counting when the drive is executing error recovery and it restarts on each command. There-
fore, each command’s total recovery time is subject to the recovery time limit. Note: A recovery time limit
of 0 will use the drive’s default value of FF FF. Minimum recovery time limit is achieved by setting the
Recovery Time Limit field to 00 01.
7.3 SCSI systems errors
Information on the reporting of operational errors or faults across the interface is given in the SCSI Interface
Product Manual. Message Protocol System is described in the SCSI Command Reference Manual. Several of
the messages are used in the SCSI systems error management system. The Request Sense command
returns information to the host about numerous kinds of errors or faults. The Receive Diagnostic Results
reports the results of diagnostic operations performed by the drive.
Status returned by the drive to the Initiator is described in the SCSI Interface Product Manual. Status reporting
plays a role in the SCSI systems error management and its use in that respect is described in sections where
the various commands are discussed.
Table 3: Read and write retry count maximum recovery times [1]
Read retry
count [1] Maximum recovery time per
LBA (cumulative, msec) Write retry
count Maximum recovery time per
LBA (cumulative, msec)
0 77.7 0 35.9
1 89.7 1 53.8
2 305 2 83.7
3 353 3 101.7
4 401 4 179.4
5 419 5 (default) 221.3
6 466
7 586
8 676
9 724
10 777
11 (default) 1,591