Determining Which RAID Level to Use

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Determining Which RAID Level to Use
The type of RAID unit (array) that you create depends on your needs. You might want to maximize speed of access, total amount of storage, or redundant protection of data. Each type of RAID unit offers a different blend of these characteristics.
The following table summarizes RAID configuration types.

RAID Configuration Types
RAID Type | Description
RAID 0 | Provides performance, but no fault tolerance.
RAID 1 | Provides fault tolerance and a read speed advantage over non-RAID disks.
RAID 5 | Provides performance, fault tolerance, and high storage efficiency. RAID 5 units can tolerate one drive failing before losing data.
RAID 6 | Provides very high fault tolerance with the ability to protect against two consecutive drive failures. Performance and efficiency increase with higher numbers of drives.
RAID 10 | Provides a combination of striped and mirrored units for fault tolerance and high performance.
RAID 50 | Provides a combination of RAID 5 and RAID 0. RAID 50 provides high fault tolerance and performance.
Single Disk | Not a RAID type - but supported as a configuration. Provides maximum disk capacity with no redundancy.

You can create one or more units, depending on the number of drives you install. The following table provides possible configurations based on your number of drives.

Possible Configurations Based on Number of Drives
Number of Drives | Possible RAID Configurations
1 | Single disk
2 | RAID 0 or RAID 1
3 | RAID 0 RAID 1 with hot spare RAID 5
4 | RAID 5 with hot spare RAID 10 Combination of RAID 0, RAID 1, single disk
5 | RAID 6 RAID 5 with hot spare RAID 10 with hot spare Combination of RAID 0, RAID 1, hot spare, single disk
6 or more | RAID 6 RAID 6 with hot spare RAID 50 Combination of RAID 0, 1, 5, 6,10, hot spare, single disk

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