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CHEETAH 15K.7 SAS PRODUCT MANUAL, REV. F 34
[1] These values are subject to change.
Setting these retry counts to a value below the default setting could result in degradation of the 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 253.11 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 Recov-
ery Time Limit field to 00 01.
9.3 SAS SYSTEM ERRORS
Information on the reporting of operational errors or faults across the interface is given in the SAS Interface Manual. The
SSP Response 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 SAS Interface Manual. Status reporting plays a role in systems
error management and its use in that respect is described in sections where the various commands are discussed.
Table 6 Read and write retry count maximum recovery times [1]
READ RETRY
COUNT
MAXIMUM RECOVERY TIME PER LBA
(CUMULATIVE, MSEC)
WRITE
RETRY
COUNT
MAXIMUM RECOVERY TIME PER LBA
(CUMULATIVE, MSEC)
0 51.87 0 23.94
1 59.85 1 35.91
2 203.49 2 39.9
3 231.42 3 51.87
4 295.26 4 79.8
5 327.18 5 (default) 107.73
6 359.10
7 446.88
8 538.65
9 570.57
10 598.50
11 (default) 1,534.97