Using drive capacity efficiently – Avago Technologies 3ware SAS 9750-16i4e User Manual
Page 25
Understanding RAID Levels and Concepts
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17
Using Drive Capacity Efficiently
Because the capacity of each drive is limited to the capacity of the smallest
drive in the unit, use drives of the same capacity in a unit.
The total unit 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
Table 3: Possible Configurations Based on Number of Drives
Number of
Drives
Possible RAID Configurations
Table 4: Drive Capacity
RAID Level
Capacity
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)
RAID 50
(number of drives – number of groups of drives) X (capacity of
the smallest drive)