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Guidelines for RAID Groups
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RAID Types and Tradeoffs
Guidelines for RAID Groups
To decide when to use a RAID5 Group, RAID 3 Group, mirror (that
is, a RAID1 mirrored pair or RAID 1/0 Group, a RAID 0 Group,
individual disk unit, or hot spare), you need to weigh these factors:
•Importance of data availability
•Importance of performance
•Amount of data stored
•Cost of disk space
The following guidelines will help you decide on RAID types.
Use a RAID5 Group (individual access array) for applications
where
•Data availability is very important.
•Large volumes of data will be stored.
•Multitask applications use I/O transfers of different sizes.
•Excellent read and good write performance is needed (write
performance is very good with write caching).
•You want the flexibility of multiple LUNs per RAID Group.
Use a RAID3 Group (parallel access array) for applications where
•Data availability is very important.
•Large volumes of data will be stored.
•A single-task application uses large I/O transfers (more than 64
Kbytes). The operating system must allow transfers aligned to
start at disk addresses that are multiples of 2 Kbytes from the start
of the LUN.
Use a RAID1 mirrored pair for applications where
•Data availability is very important.
•Speed of write access is important and write activity is heavy.
Use a RAID1/0 Group (mirrored nonredundant array) for
applications where
•Data availability is critically important.
•Overall performance is very important.