User`s guide

Appendix B: Understanding RAID ● 71

RAID 5EE Arrays

A RAID 5EE array—also known as a hot space—is similar to a RAID 5 array except that it

includes a distributed spare drive 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 this figure, 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

Drive Segment Size

(Smallest Disk Drive)

Disk Drive 2

Disk Drive 3

Disk Drive 4

Disk Drive 1

1S... P

2 P ... 449

S3... S

P 4 ... 500

Unused Space = 150 GB

Disk Drives in Logical Drive RAID 5EE Logical Drive = 750 GB plus

Parity and Spare

Unused Space = 150 GB