Auto Rebuilding; Adjustable Rebuild Priority - Areca ARC-1110 User Manual

INTRODUCTION

1.4.4 Auto Rebuilding

If a hot spare is available, the rebuild starts automatically when
a drive fails. ARC-11xx/12xx RAID adapters automatically and
transparently rebuild failed drives in the background at user-de-
finable 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 ARC-11xx/12xx RAID adapters will automatically restart the
system and the rebuild process if the system is shut down or
powered off abnormally during a reconstruction procedure condi-
tion.
When a disk is Hot Swapped, although the system is function-
ally 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 subsys-
tem. The ARC-11xx/12xx RAID adapters allow the user to select
the rebuild priority to balance volume access and rebuild tasks
appropriately. The Background Task Priority is a relative indication
of how much time the controller devotes to a background opera-
tion, such as rebuilding or migrating.
The RAID subsystem allows user to choose the task priority (Ultra
Low (5%), Low (20%), Medium (50%), High (80%)) to balance
volume set access and background tasks appropriately. For high
array performance, specify an Ultra Low value. Like volume ini-
tialization, after a volume rebuilds, it does not require a system
reboot.
22