Appendix B: Selecting the Best RAID Level
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158
RAID 5EE Logical Drives
A RAID 5EE logical drive—also referred to as a
hot space
—is similar to a RAID 5 logical drive
except that it includes a
distributed spare
drive and must be built from a minimum of four disk
drives.
Unlike a hot spare (see
page 54
), 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 logical drive is rebuilt following a disk drive failure.
A RAID 5EE logical drive 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 example, 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
250 GB
400 GB
400 GB
Drive Segment Size (Smallest Disk Drive)
Disk Drive 2
Disk Drive 3
Disk Drive 4
Disk Drive 1
1 S ...
P
2 P ... 449
S 3 ...
S
P 4 ... 500
Unused Space = 150 GB
Disk Drives in Logical Drive
Unused Space = 150 GB
= 500 GB plus Parity and Spare
RAID 5EE
Logical Drive
