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38 Cheetah 36XL Product Manual, Rev. E
[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 378 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. Therefore,
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,
part number 75789509. Message Protocol System is described in the
SCSI Interface Product
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 Diag-
nostic 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)
078 066
190 184
2306 2126
3330 3144
4378 4252
5426 5294
6546 6498
7696 7516
8720 8546
9774 9564
10 846 10 1200
11 (default) 1569 11 1218
12 1260
13 1278
14 1386
15 (default) 1428