3Ware 9650SE-2LPB-10 User Manual page 21

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Table 4: Possible Configurations Based on Number of Drives
# Drives Possible RAID Configurations
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
Using Drive Capacity Efficiently
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:
Table 5: 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)
Through drive coercion, the capacity used for each drive is rounded down so
that drives from differing manufacturers are more likely to be able to be used
Understanding RAID Concepts and Levels
11