AMCC 720-0138-00 manual Single Disk, Hot Spare

Understanding RAID Concepts and Levels

RAID 10

RAID 10 is a combination of striped and mirrored arrays for fault tolerance and high performance.

When drives are configured as a striped mirrored array, the disks are configured using both RAID 0 and RAID 1 techniques, thus the name RAID 10 (see Figure 4). A minimum of four drives are required to use this technique. The first two drives are mirrored as a fault tolerant array using RAID 1. The third and fourth drives are mirrored as a second fault tolerant array using RAID 1. The two mirrored arrays are then grouped as a striped RAID 0 array using a two tier structure. Higher data transfer rates are achieved by leveraging TwinStor and striping the arrays.

In addition, RAID 10 arrays offer a higher degree of fault tolerance than other types of RAID levels (such as RAID 1 and RAID 5), since the array can sustain multiple drive failures without data loss. Please note that if both halves of a mirrored pair in the RAID 10 array fail, then all of the data will be lost.

Figure 4. RAID 10 Configuration Example

Single Disk

A single drive can be configured as a unit through 3ware software. (3DM 2 or CLI). Like disks in other RAID configurations, single disks contain 3ware Disk Control Block (DCB) information and are seen by the OS as available units.

Single drives are not fault tolerant and therefore not recommended for high availability systems unless additional precautions are taken to prevent system hangs and data loss.

Hot Spare

A hot spare is a single drive, available online, so that a redundant unit can be automatically rebuilt in case of drive failure.

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