HP Smart Array 6i Controller and 128MB BBWC - Manual (Page 42)

42 HP Smart Array 6i Controller User Guide
For any configuration except RAID 0, further protection against data loss can be
achieved by assigning a drive as an online spare (or hot spare). This drive
contains no data and is connected to the same controller as the array. When any
other physical drive in the array fails, the controller automatically rebuilds
information that was originally on the failed drive to the online spare. The system
is thus restored to full RAID-level data protection, although it now no longer has
an online spare. (However, in the unlikely event that another drive in the array
fails while data is being rewritten to the spare, the logical drive will still fail.)
When you configure an online spare, it is automatically assigned to all logical
drives in the same array. Additionally, you do not need to assign a separate
online spare to each array. Instead, you can configure one hard drive to be the
online spare for several arrays if the arrays are all on the same controller.
Fault-Tolerance Methods
Several fault-tolerance methods exist. Those most often used with Smart Array
controllers are hardware-based RAID methods.
Two alternative fault-tolerance methods that are sometimes used are also
described ("Alternative Fault-Tolerance Methods" on page
48 ). However,
hardware-based RAID methods provide a much more robust and controlled fault-
tolerance environment, so these alternative methods are seldom used.
Hardware-Based Fault-Tolerance Methods
The hardware-based methods that are recommended for use with Smart Array
controllers are:
•
RAID 0—Data Striping only (no fault tolerance)
•
RAID 1+0—Drive Mirroring
•
RAID 5—Distributed Data Guarding
•
RAID ADG—Advanced Data Guarding
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