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E-24 Understanding Drive Arrays
Writer: Rickard Project: Compaq Smart Array 3200 Controller Reference Guide Comments: 340862-002
File Name: L-APPE.DOC Last Saved On: 12/7/98 9:30 AM
COMPAQ CONFIDENTIAL - NEED TO KNOW REQUIRED
Interim Data Recovery
In RAID 5, RAID 4, or RAID 1 fault-tolerant configurations, if a drive fails, the
system continues to operate in an interim data recovery mode. For example, if
you selected RAID 5 for a logical drive with four physical drives and one of the
drives fails, the system continues to process I/O requests, but at a reduced
performance level. Replace the failed drive as soon as possible to restore
performance and full fault tolerance for that logical drive. See Appendix G for
more information on drive failure recovery.
Automatic Data Recovery
After you replace a failed drive, automatic data recovery reconstructs the data
and places it on the replaced drive. This enables a rapid recovery to full
operating performance without interrupting normal system operations.
In general, the time required for a rebuild is approximately 15 minutes per GB.
However, the actual rebuild time depends on the rebuild priority set for the
amount of I/O activity occurring during the rebuild operation, disk drive speed,
and the number of drives in the array (RAID 4 and RAID 5). In RAID 4 and
RAID 5 configurations, the rebuild time varies from 10 minutes per GB for
three drives to 20 minutes per GB for 14 drives (using 9-GB Wide-Ultra hard
drives).
NOTE: You must specify RAID 5, RAID 4, or RAID 1 through the Array
Configuration Utility to make the recovery feature available. The drive failure
alert system and automatic data recovery are functions of the Smart Array
3200 Controller; they function independently of the operating system.