IBM ATA 133, User Manual

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Chapter 2 Introduction to RAID 9
Selecting a RAID Level
To ensure the best performance, you should select the optimal RAID level when you
create a system drive. The optimal RAID level for your disk array depends on the
following factors:
•
Number of drives in the disk array
•
Capacity of the drives in the array
•
Need for data redundancy
•
Disk performance requirements
Table 2-4 describes the factors you need to consider when selecting a RAID level.
Table 2-4. Factors to Consider When Selecting a RAID Level
Level Description and Use Pros Cons Number
of Drives
Fault
Tolerant
0 Data divided in blocks
and distributed
sequentially (pure
striping). Use for non-
critical data that
requires high
performance. High data
throughput for
large files. No fault
tolerance. All
data lost if any
drive fails. One to
Four
No
1 Data duplicated on
another disk
(mirroring). Use for
read-intensive fault-
tolerant systems. 100 percent
data
redundancy. Doubles disk
space required.
Reduced
performance
during rebuilds. Two Yes
10 Data divided in blocks
and distributed
sequentially and each
block is duplicated to
another disk. 100 percent
data
redundancy and
High data
throughput. Four drives
required. Four Yes
Assigning RAID Levels
Only one RAID level can be assigned to each array. Table 2-5 lists the drives required per
RAID level.
Table 2-5. Drives Required Per RAID Level
RAID
Level
Minimum Number of
Physical Drives
Maximum Number of Physical
Drives
0 One Four
1 Two Two
10 Four Four