Avago Technologies MegaRAID SATA 150-4 (523) - Manual (Page 41)

RAID Configuration Strategies 2-19
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Figure 2.6 RAID 50 Logical Drive
2.6 RAID Configuration Strategies
The most important factors in RAID array configuration are:
•
Logical drive availability (fault tolerance)
•
Logical drive performance
•
Logical drive capacity
You cannot configure a logical drive that optimizes all three factors, but
it is easy to choose a logical drive configuration that maximizes one
factor at the expense of another factor. For example, RAID 1 (mirroring)
provides excellent fault tolerance, but requires a redundant drive. The
following subsections describe how to use the RAID levels to maximize
logical drive availability (fault tolerance), logical drive performance, and
logical drive capacity.
2.6.1 Maximizing Fault Tolerance
Fault tolerance is achieved through the ability to perform automatic and
transparent rebuilds using hot spare drives and hot swaps. A hot spare
drive is an available, unused online drive that the RAID controller
instantly plugs into the system when an active drive fails. After the hot
spare is automatically moved into the RAID array, the failed drive is
automatically rebuilt on the spare drive. The RAID array continues to
handle requests while the rebuild occurs.
Segment 1 Segment 2
Segment 5 Segment 6
RAID 0
RAID 50
(Segment 1, 2) Segment 3 Segment 4
Segment 8 Segment 7
Segment 9 Segment 10 Segment 11 Segment 12
(Segment 5, 6)
(Segment 9, 10) (Segment 11, 12)
(Segment 7, 8)
(Segment 3, 4)
RAID 5 RAID 5