Understanding RAID Concepts and Levels

Available RAID Configurations

The following RAID levels and configurations are available for drives attached to a 9590SE-4ME 3ware RAID controller:

RAID 0

RAID 1

RAID 5

RAID 10

Single Disk

Hot Spare

For how to configure RAID units, see “Configuring a New Unit” on page 34.

RAID 0

RAID 0 provides improved performance, but no fault tolerance. Since the data is striped across more than one disk, RAID 0 disk arrays achieve high transfer rates because they can read and write data on more than one drive simultaneously. The stripe size is configurable during unit creation. Requires a minimum of two drives.

When drives are configured in a striped disk array (see Figure 1), large files are distributed across the multiple disks using RAID 0 techniques.

Striped disk arrays give exceptional performance, particularly for data intensive applications such as video editing, computer aided design and geographical information systems.

RAID 0 arrays are not fault tolerant. The loss of any drive results in the loss of all the data in that array, and can even cause a system hang, depending on your operating system. RAID 0 arrays are not recommended for high availability systems unless additional precautions are taken to prevent system hangs and data loss.

Figure 1. RAID 0 Configuration Example

RAID 1

RAID 1 provides fault tolerance and a speed advantage over non-RAID disks. Also known as a mirrored array. Mirroring is done on pairs of drives. Mirrored disk arrays write the same data to two different drives using RAID 1 algorithms (see Figure 2). This gives your system fault tolerance by

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AMCC 720-0138-00 manual Available RAID Configurations, Raid