Adaptec 2820SA User Guide - Page 71

RAID 5EE Arrays, improves the speed at which the array is rebuilt following a disk drive failure.

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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 1 250 GB Drive Segment Size (Smallest Disk Drive) Disk Drive 2 250 GB Disk Drive 3 400 GB Disk Drive 4 400 GB Disk Drives in Logical Drive Disk Drive 1 1 S ... P Disk Drive 2 2 P ... 449 Disk Drive 3 S 3 ... S Unused Space = 150 GB Disk Drive 4 P 4 ... 500 Unused Space = 150 GB RAID 5EE Logical Drive = 750 GB plus Parity and Spare

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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
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
RAID 5EE Logical Drive = 750 GB plus
Parity and Spare
Unused Space = 150 GB