LSI MegaRAID Express 500 - Manual (Page 23)

Chapter 2 Introduction to RAID 9
Disk Rebuild
You rebuild a disk drive by recreating the data that had been stored on the drive before
the drive failed.
Rebuilding can be done only in arrays with data redundancy such as RAID level 1, 3, 5,
10, 30, and 50.
Standby (warm spare) rebuild is employed in a mirrored (RAID 1) system. If a disk drive
fails, an identical drive is immediately available. The primary data source disk drive is the
original disk drive.
A hot spare can be used to rebuild disk drives in RAID 1, 3, 5, 10, 30, or 50 systems. If a
hot spare is not available, the failed disk drive must be replaced with a new disk drive so
that the data on the failed drive can be rebuilt.
The MegaRAID Express 500 controller automatically and transparently rebuilds failed
drives with user-definable rebuild rates. If a hot spare is available, the rebuild starts
automatically when a drive fails. MegaRAID Express 500 automatically restarts the
system and the rebuild if the system goes down during a rebuild.
Rebuild Rate The rebuild rate is the fraction of the compute cycles dedicated to rebuilding failed drives.
A rebuild rate of 100 percent means the system is totally dedicated to rebuilding the failed
drive.
The MegaRAID Express 500 rebuild rate can be configured between 0% and 100%. At
0%, the rebuild is only done if the system is not doing anything else. At 100%, the rebuild
has a higher priority than any other system activity.
Physical Array A RAID array is a collection of physical disk drives governed by the RAID management
software. A RAID array appears to the host computer as one or more logical drives.