Specifications

SCSI to SATA RAID Subsystem | Administrator’s Manual Data Integrity | en 153
Bosch Security Systems F.01U.027.802 | V1 | 2006.11
The Fault Scenario:
Spare drives accelerate rebuild of a logical drive. In the example as described below, multiple
faults can occur at the same time making the array exposed to the risk of data loss:
• There is only one Global Spare in a RAID subsystem.
• That Global Spare has been used to rebuild a logical drive.
• The failed drive is swapped out and replaced by a new one.
• Chances are system administrators forgot to configure the replacement drive as a spare.
• A member of another logical drive fails.
• The subsystem has no spare left. Performance decreases for a considerable portion of
system resources has to be conducted to generate data from the remaining members of
the logical drive. If yet another member fails in the logical drive, data is lost.
The chance of failing two drives increases when a failed drive in the array cannot be replaced
immediately for the lack of spare drives.
The Function
If a drive has a capacity smaller or apparently larger than the members of configured arrays,
the controller may avoid using it as a global spare.
Enable the function and reset the controller for the configuration to take effect.