Raid Configuration Strategies; Raid 0; Raid 60 Overview - Lenovo ThinkServer RD240 Software User's Manual

2.6

RAID Configuration Strategies

Table 2.12

RAID 60 Overview

Weak Points
Drives
Figure 2.12 shows a RAID 6 data layout. The second set of parity drives
are denoted by Q. The P drives follow the RAID 5 parity scheme.
Figure 2.12 RAID 60 Level Virtual Drive
RAID
Segment 1
Segment 2
60
Segment 8
Parity (Q3-Q4)
Parity (Q11–Q12)
Parity (P11-P12)
Parity (P15-P16)
Segment 15
Note: Parity is distributed across all drives in the drive group.
The most important factors in RAID drive group configuration are:
•
Virtual drive availability (fault tolerance)
•
Virtual drive performance
•
Virtual drive capacity
You cannot configure a virtual drive that optimizes all three factors, but it
is easy to choose a virtual 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
RAID Configuration Strategies
Not well suited to tasks requiring lot of writes. A RAID
60 virtual drive has to generate two sets of parity data
for each write operation, which results in a significant
decrease in performance during writes. Drive
performance is reduced during a drive rebuild.
Environments with few processes do not perform as
well because the RAID overhead is not offset by the
performance gains in handling simultaneous processes.
RAID 6 costs more because of the extra capacity
required by using two parity blocks per stripe.
A minimum of 8
Parity (Q1-Q2) Parity (P1-P2)
Parity (P3-P4) Segment 7
Segment 11 Segment 12
Segment 16
Parity (Q15-Q16)
RAID 6

RAID 0

Segment 4
Segment 3 Parity (Q3-Q4)
Segment 6 Parity (Q5-Q6)
Parity (P5-P6)
Parity (Q9–Q10)
Segment 9
Parity (P9-P10)
Parity (P13-P14) Segment 14
Segment 13
RAID 6
Parity (P3-P4)
Segment 5
Segment 10
Parity (Q13-Q14)
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