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Understanding RAID Levels and Concepts

17

To make the most efficient use of drive capacity, it is advisable to use drives 
of the same capacity. This is because the capacity of each drive is limited to 
the capacity of the smallest drive in the unit. 

The total array capacity is defined as follows:

                                      

3

RAID  0

RAID 1 with hot spare

RAID 5

4

RAID 5 with hot spare

RAID 10

Combination of RAID 0, RAID 1, single disk

5

RAID  6

RAID 5 with hot spare

RAID 10 with hot spare

Combination of RAID 0, RAID 1, hot spare, single disk

6 or more

RAID 6

RAID 6 with hot spare

RAID 50

Combination of RAID 0, 1, 5, 6,10, hot spare, single disk

Single Disk

Capacity of the drive

RAID 0

(number of drives) X (capacity of the smallest drive)

RAID 1 

Capacity of the smallest drive

RAID 5

(number of drives - 1) X (capacity of the smallest drive)

Storage efficiency increases with the number of disks:

storage efficiency = (number of drives -1)/(number of drives)

RAID 6

(number of drives - 2) x (capacity of the smallest drive)

RAID 10

(number of drives / 2) X (capacity of smallest drive)