Raid 5 Algorithms For Distributing Stripes And Parity - Novell LINUX ENTERPRISE SERVER 10 SP2 - STORAGE ADMINISTRATION GUIDE 05-15-2009 Administration Manual

6.1.8 RAID 5 Algorithms for Distributing Stripes and Parity

RAID 5 uses an algorithm to determine the layout of stripes and parity. The following table
describes the algorithms.
RAID 5 Algorithms
Table 6-7
Algorithm
Left Asymmetric
Left Symmetric
Right Asymmetric
Right Symmetric
80 SLES 10 SP2: Storage Administration Guide
EVMS Type Description
1 Stripes are written in a round-robin fashion from the first to last
member segment. The parity's position in the striping sequence
moves in a round-robin fashion from last to first. For example:
sda1 sdb1 sdc1 sde1
0 1
3 4
6 p
p 9
12 13
2 This is the default setting and is considered the fastest method for
large reads.
Stripes wrap to follow the parity. The parity's position in the striping
sequence moves in a round-robin fashion from last to first. For
example:
sda1 sdb1 sdc1 sde1
0 1
4 5
8 p
p 9
12 13
3 Stripes are written in a round-robin fashion from the first to last
member segment. The parity's position in the striping sequence
moves in a round-robin fashion from first to last. For example:
sda1 sdb1 sdc1 sde1
p 0
3 p
6 7
9 10
p 12
4 Stripes wrap to follow the parity. The parity's position in the striping
sequence moves in a round-robin fashion from first to last. For
example:
sda1 sdb1 sdc1 sde1
p 0
5 p
7 8
9 10
p 12
2 p
p 5
7 8
10 11
14 p
2 p
p 3
6 7
10 11
14 p
1 2
4 5
p 8
11 p
13 14
1 2
3 4
p 6
11 p
13 14