User manual

Chapter 3: RaQ 4 Server Management
36 Cobalt RaQ 4 User Manual
Support for RAID-1 (RaQ 4r configuration only)
A redundant array of independent disks (RAID) is a way of storing the same data
in different places (thus, redundantly) on multiple hard disk drives. A RAID
appears to the operating system to be a single virtual hard disk drive.
Redundancy means that there is protection against the failure of any single hard
disk drive. Redundant data is used by a RAID system in the event of a failure;
this redundant data can either be a mirror copy or parity data used to reconstruct
the actual data.
There are a variety of different types and implementations of RAID, each with its
own advantages and disadvantages. The RaQ 4r implements RAID Level 1
(RAID-1), also known as disk mirroring, which consists of a primary hard disk
drive and a secondary hard disk drive; the secondary hard disk drive is an exact
copy or “mirror image” of the primary hard disk drive.
Although RAID can protect your data in case of a hard-disk-drive failure, it does
not protect against operator and administrator (human) error, or against loss due
to programming bugs.
The RaQ 4 server implements RAID services through software. Each hard disk
drive has its own independent master channel to allow high performance without
extra RAID hardware.
You do not need to enable RAID-1 on the RaQ 4r; it is enabled by default. You
cannot disable RAID-1 on the RaQ 4r.
There are two possible causes for RAID failure on the RaQ 4r:
• Hardware failure . If a hard disk drive fails, the RaQ 4r can function with
one hard disk drive, but the server can no longer provide disk mirroring. To
restore RAID service, you must shut down the RaQ 4 and replace the failed
hard disk drive.
• Software failure . The RAID software should not fail. If it does, the likely
cause is a failure of the whole kernel, in which case the RaQ 4r just reboots.
In case of a failed hard disk drive, you will have to replace the hard disk drive.
For more information on replacing a hard disk drive, see “Upgrading your
RaQ 4” on page 161.
For a failed drive, Active Monitor indicates that the Left or Right hard disk drive
has failed (“Right” and “Left” are in relation to looking at server with the front
blue panel facing you.)