Novell LINUX ENTERPRISE SERVER 10 - STORAGE ADMINISTRATION GUIDE 7-2007, Administration Manual

Page: 64 / 108

64 SLES 10 Storage Administration Guide
no
vd
ocx
(e
n)
6 Ap
ril 20
07
Table 6-7
RAID 5 Algorithms
For information about the layout of stripes and parity with each of these algorithms, see Linux
RAID-5 Algorithms (http://www.accs.com/p_and_p/RAID/LinuxRAID.html) .
Algorithm EVMS Type Description
Left Asymmetric 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 2 p
3 4 p 5
6 p 7 8
p 9 10 11
12 13 14 p
Left Symmetric 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 2 p
4 5 p 3
8 p 6 7
p 9 10 11
12 13 14 p
Right Asymmetric 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 1 2
3 p 4 5
6 7 p 8
9 10 11 p
p 12 13 14
Right Symmetric 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 1 2
5 p 3 4
7 8 p 6
9 10 11 p
p 12 13 14