Compaq 226593-B21 - Smart Array 5i RAID Controller User Manual page 91

Drive Arrays and Fault Tolerance
Table C-1: Summary of RAID Methods
Tolerates failure
of one physical
drive?
Tolerates
simultaneous
failure of >one
physical drive?
Read
performance
Write
performance
Relative cost
*Values for usable drive space are calculated with these assumptions:
•
All physical drives in the array have the same capacity.
•
Online spares are not used.
•
No more than 14 physical drives are used for RAID 5. (This number is
recommended so that the risk of logical drive failure is kept low. See
Appendix D for further information.)
Table C-2: Choosing a RAID Method
Most Important
Cost effectiveness
I/O performance
C-10 Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache Enabler User Guide
RAID 0 RAID 1+0
No Yes
No Only if no two
failed drives are
in a mirrored
pair
High High
High Medium
Low High
Also Important
I/O performance
I/O performance
Cost effectiveness
Fault tolerance
continued
RAID 5
Yes
No
High
Low
Medium
Suggested RAID
Level
RAID 1+0
RAID 5 (RAID 0 if fault
tolerance is not
required)
RAID 5 (RAID 0 if fault
tolerance is not
required)
RAID 1+0