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Introduction
1-16
1.4.4.2 Hot-Swap Disk Drive Support
The RAID subsystem has built the protection circuit to support the replace-
ment of UDMA hard disk drives without having to shut down or reboot the
system. The removable hard drive tray can deliver “hot swappable,” fault-
tolerant RAID solutions at prices much less than the cost of conventional
SCSI hard disk RAID subsystems. We provide this feature for subsystems to
provide the advanced fault tolerant RAID protection and “online” drive
replacement.
1.4.4.3 Hot-Swap Disk Rebuild
A Hot-Swap function can be used to rebuild disk drives in arrays with data
redundancy such as RAID level 1(0+1), 3, 5 and 6. 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. If a hot spare is available, the
rebuild starts automatically when a drive fails. The RAID subsystem auto-
matically and transparently rebuilds failed drives in the background with user-
definable rebuild rates. The RAID subsystem will automatically restart the
system and the rebuild if the system is shut down or powered off abnormally
during a reconstruction procedure condition.
When a disk is Hot Swap, al-
though 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.