HP 226593-B21 Smart Array 5i Plus Controller and Battery Backed Write Cache En - Page 91

Table C-1, Summary of RAID Methods, Choosing a RAID Method, RAID 0, Most Important, Suggested RAID

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Drive Arrays and Fault Tolerance Table C-1: Summary of RAID Methods continued RAID 0 RAID 1+0 RAID 5 Tolerates failure No of one physical drive? Yes Yes Tolerates No simultaneous failure of >one physical drive? Only if no two No failed drives are in a mirrored pair Read performance High High High Write performance High Medium Low Relative cost Low High Medium *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 Also Important I/O performance I/O performance I/O performance Cost effectiveness Fault tolerance 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 C-10 Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache Enabler User Guide

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Drive Arrays and Fault Tolerance
C-10
Compaq Smart Array 5i Plus Controller and Battery Backed Write Cache Enabler User Guide
Table C-1:
Summary of RAID Methods
continued
RAID 0
RAID 1+0
RAID 5
Tolerates failure
of one physical
drive?
No
Yes
Yes
Tolerates
simultaneous
failure of >one
physical drive?
No
Only if no two
failed drives are
in a mirrored
pair
No
Read
performance
High
High
High
Write
performance
High
Medium
Low
Relative cost
Low
High
Medium
*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
Also Important
Suggested RAID
Level
I/O performance
RAID 1+0
Cost effectiveness
I/O performance
RAID 5 (RAID 0 if fault
tolerance is not
required)
I/O performance
Cost effectiveness
RAID 5 (RAID 0 if fault
tolerance is not
required)
Fault tolerance
RAID 1+0