HP A7143A RAID160 SA Controller Support Guide, February 2007

RAID Technology Overview
Summary of RAID Methods
Chapter 1
20
Summary of RAID Methods
Table 1-1 summarizes the important features of the different RAID configurations that are supported by the
Smart Array Controllers. The decision chart in Table 1-2 on page 21 can help you determine 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 96% 50% to 93%
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
28 physical disks are used per array for RAID 5.