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INTRODUCTION
22
1.4.4 Auto Rebuilding
If a hot spare is available, the rebuild starts automatically when
a drive fails. The SATA RAID controllers automatically and trans-
parently rebuild failed drives in the background at user-denable
rebuild rates.
If a hot spare is not available, the failed disk drive must be re-
placed with a new disk drive so that the data on the failed drive
can be automatically rebuilt and so that fault tolerance can be
maintained.
The SATA RAID controllers will automatically restart the system
and the rebuild process if the system is shut down or powered off
abnormally during a reconstruction procedure condition.
When a disk is hot swapped, although the system is functionally
operational, the system may no longer be fault tolerant. Fault
tolerance will be lost until the removed drive is replaced and the
rebuild operation is completed.
During the automatic rebuild process, system activity will contin-
ue as normal, however, the system performance and fault toler-
ance will be affected.
1.4.5 Adjustable Rebuild Priority
Rebuilding a degraded volume incurs a load on the RAID sub-
system. The SATA RAID controllers allow the user to select the
rebuild priority to balance volume access and rebuild tasks ap-
propriately. The Background Task Priority is a relative indication of
how much time the controller devotes to a background operation,
such as rebuilding or migrating.
The SATA RAID controller allows user to choose the task priority
(Ultra Low (5%), Low (20%), Medium (50%), High (80%)) to bal-
ance volume set access and background tasks appropriately. For
high array performance, specify an Ultra Low value. Like volume
initialization, after a volume rebuilds, it does not require a system
reboot.