AMCC 9590SE-4ME Manual De Usuario

Chapter 1. Introduction to the 3ware Command Line Interface

14

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:

                                      

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 
as spares for each other. The capacity used for each drive is rounded down to 
the nearest GB for drives under 45 GB (45,000,000,000 bytes), and rounded 
down to the nearest 5 GB for drives over 45 GB. For example, a 44.3 GB 
drive will be rounded down to 44 GB, and a 123 GB drive will be rounded 
down to 120 GB. For more information, see the discussion of drive coercion 
under “Creating a Hot Spare” on page 42.

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 10

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