User`s guide

Appendix B: Understanding RAID ● 85

RAID 5EE Arrays

Note: RAID 5EE is an upgrade feature; if the RAID 5EE feature is

locked, see Adding Enhanced Features on page 20 for information on

purchasing a feature key.

A RAID 5EE array is similar to a RAID 5 array except that it includes a

distributed spare drive (see below) and must be built from a minimum

of four disk drives. The maximum number of disk drives is sixteen.

Unlike a hot spare, a distributed spare is striped evenly across the disk

drives with the stored data and parity data, and can’t be shared with

other logical disk drives. A distributed spare improves the speed at

which the array is rebuilt following a disk drive failure.

A RAID 5EE array protects your data and increases read and write

speeds. However, capacity is reduced by two disk drives’ worth of space,

which is for parity data and spare data.

In the example below, S represents the distributed spare, P represents

the distributed parity data.

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

250 GB

400 GB

isk Drives in Logical Drive

Disk Drive 1

Disk Drive 2

Disk Drive 3

Disk Drive 4

RAID 5EE Logical Drive = 500 GB plus Parity and Spa

Not Used

4 500

449

P...

...

Unused Space: 150 GB

Drive Segment Size (Smallest Disk Drive)