HP A7143A RAID160 SA Controller Support Guide

RAID Technology Overview
Summary of RAID Methods
Chapter 1 25
Summary of RAID Methods
Table 1-1 summarizes the important features of the different RAID
configurations that are supported by the HP RAID160 SA controller. The
decision chart in Table 1-2 on page 26. may help with determining which
option is best for your computing environment.
Table 1-1 Summary of RAID Methods
RAID 0 RAID 1 RAID1+0 RAID 5 RAID ADG
Alternative name Striping
(no fault
tolerance)
Mirroring Mirroring and
Striping
Distributed
Data
Guarding
Advanced
Data
Guarding
Usable disk drive
space*
100% 50% 50% 67% to 93% 50% to 96%
Usable disk drive space
formula
n n/2 n/2 (n-1)/n (n-2)/n
Minimum number of
physical disks
12 4 3 4
Tolerates failure of one
physical disk?
No Yes Yes Yes Yes
Tolerates simultaneous
failure of more than one
physical disk?
No No Only if no two
failed disks
are in a
mirrored pair
No Yes
Read performance High High High High High
Write performance High Medium Medium Low Low
Relative cost Low High High Medium Medium
*Values for usable disk drive space are calculated with these assumptions: (1) All physical disks in
the array have the same capacity; (2) Online spares are not used; (3) No more than 14 physical
disks are used per array for RAID 5; (4) No more than 56 disks are used with RAID ADG.