5.6. RAID. LaCie 5big Network

LaCie 5big Network

User Manual

RAID and Disks

page 55

5.6. RAID 10

RAID 10 (also called RAID 1+0) is another RAID level that combines the attributes of other levels, specifically RAID 1 and RAID 0. It is a

“stripe of mirrored sets”, meaning that data is striped across two mirrored arrays (

Fig. 88 ). The Striping occurs between arrays and the

mirroring occurs within the same array, which makes the rebuilding very fast. RAID 10 arrays should have disks in multiples of four. For

LaCie products with five disks, in a RAID 10 array, the fifth disk will either be a spare or will be unused. See the diagram at right.

In a RAID 10 array, one disk from each mirrored pair can fail with no data loss. However, the working disk in an array with a failed disk becomes a weak point for the entire array. If the second disk in a mirrored pair fails, the entire array is lost.

Applications

RAID 10 provides good speeds because of RAID 0 striping, but cuts the available capacity of a device in half (assuming all disks in the array have the same capacity).

How RAID 10 Capacity Is Calculated

Each disk in a RAID 10 system should have the same capacity.

Storage capacity in a RAID 10 configuration is calculated by multiplying the number of drives by the disk capacity and dividing by 2, or

C = n*d/2 where:

C = available capacity n = number of disks d = disk capacity

For example, in a RAID 10 array with four drives each with a capacity of 1000GB, the total capacity of the array would be 2000GB:

C = (4*1000)/2

Fig. 88

RAID 10

A1

A3

A5

A7

Disk 1

RAID 1

A1

A3

A5

A7

Disk 2

RAID 0

A2

A4

A6

A8

Disk 3

RAID 1

A2

A4

A6

A8

Disk 4