Installation guide

Chapter 1. Introduction
11
Note
The hot spare must have at least the same capacity as the drive it
replaces.
1.1.8 Hot-Swap Disk Drive Support
The RAID subsystem has built the protection circuit to support the replacement
of SAS/SATA 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 controllers to provide the advanced
fault tolerant RAID protection and “online” drive replacement.
1.1.9 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, 1E, 3, 5, 6, and x0. 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 automatically 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, 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.
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RAID is an acronym for Redundant Array of Independent Disks. It is an array of
multiple independent hard disk drives that provide high performance and fault
tolerance. The RAID subsystem controller implements several levels of the
Berkeley RAID technology. An appropriate RAID level is selected when the
volume sets are defined or created. This decision is based on disk capacity,
data availability (fault tolerance or redundancy), and disk performance. The
following are the RAID levels which are supported in the RAID subsystem.
The RAID subsystem controller makes the RAID implementation and the disks’
physical configuration transparent to the host operating system. This means
that the host operating system drivers and software utilities are not affected,
regardless of the RAID level selected. Correct installation of the disk array and
the controller requires a proper understanding of RAID technology and the
concepts.