Drive Arrays and Fault Tolerance

 

A1

A2

 

 

 

 

L3

L1

 

L4

 

 

L2

 

L5

Figure D-4: Two arrays (A1, A2) containing five logical drives spread across five physical drives

Each logical drive in an array is distributed across all of the physical drives within the array. A logical drive can also extend across more than one port on the same controller, but it cannot extend across more than one controller.

Drive failure, although rare, is potentially catastrophic. In Figure D-4, for example, failure of any physical drive causes all logical drives in the same array to fail, and all data on the drives is lost.

To protect against data loss due to physical drive failure, logical drives are configured with fault tolerance. There are several fault-tolerance methods; those that are described in this appendix are:

•RAID 0—Data Striping only (no fault tolerance)

•RAID 1+0—Drive Mirroring

•RAID 5—Distributed Data Guarding

•RAID ADG—Advanced Data Guarding

D-4

HP Smart Array 641/642 Controller User Guide