Quantum 10K II - Manual (Page 309)

Feature Descriptions
6-8 Quantum Atlas 10K II Ultra 160/m SCSI Hard Disk Drives
6.15.3 Host Diagnostics
The Host Processor can command the drive to perform diagnostic tests and report
status using RECEIVE and SEND DIAGNOSTIC RESULTS commands. Certain
parameters can be sent to the drive to alter or enhance the performance of the
diagnostic tests specified.
6.15.4 Log Sense
Quantum implements multiple LOG SENSE pages which logically group together
parameters related to disk and subsystem activities. Monitoring this data enables
users to observe drive performance and possibly predict failures.
6.16 ERROR RECOVERY
The mode pages control all error recovery. Any error recovery that is enabled is
attempted without host intervention.
6.16.1 Seek Error Recovery
Seek error recovery is automatic if the hardware is physically able to position to the
correct track.
6.16.2 Data Read Errors
Data read errors are recovered, if possible, by one or more of the following methods:
• Correction of the data “on-the-fly” with ECC hardware.
• Re-try the operation.
• Reload read channel registers to calibrated values.
• Off-track Recovery. Use different off-track offsets and re-try.
• Use a fixed gain while retrying.
• Margin servo thresholds to facilitate seek and detent.
• Margin the error tolerance of sync mark detection.
• Force sync mark detection while retrying.
• Skip Sector Rereads. Retries, each without one of eight earlier servo blocks.
• Correction of the bad data with the software ECC algorithm.
• Switching the bias current of the MR head between retries.
• TA baseline compensation, and other TA recovery methods.