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Introduction to RAID 39
Rebuilding can be done only in arrays with data redundancy, which includes
as RAID 1, 5, 10 and 50.
A hot spare can be used to rebuild disk drives in RAID 1, 5, 10, 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.
Using hot spares, PERC 3 can automatically and transparently rebuild failed
drives with user-defined rebuild rates. If a hot spare is available, the rebuild
can start automatically when a drive fails. PERC 3 automatically restarts the
system and the rebuild if the system goes down during a rebuild.
Rebuild Rate
The rebuild rate is the percentage 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 PERC 3 rebuild rate can be configured between 0% and 100%. At 0%,
the rebuild is done only if the system is not doing anything else. At 100%,
the rebuild has a higher priority than any other system activity. The default
rebuild rate is 30%.
Hot Swap
A hot swap is the manual replacement of a defective physical disk unit while
the computer is still running. When a new drive has been installed, a
rebuild will occur automatically if it is placed in the same drive bay as the
failed drive it is replacing. PERC 3 can be configured to detect the new disks
and to rebuild the contents of the disk drive automatically.
SCSI Drive States
The SCSI drive states are listed in Table 2-3.
Table 2-3. SCSI Drive States
State Description
Online
(ONLIN)
The drive is working normally and is a part of a configured
logical drive.