5.5. RAID. LaCie 5big Network

LaCie 5big Network

User Manual

RAID and Disks

page 54

5.5. RAID 6

In RAID 6, data is striped across all disks (minimum of four) and a two parity blocks for each data block (p and q in

Fig. 87 ) is written

on the same stripe. If one physical disk fails, the data from the failed disk can be rebuilt onto a replacement disk. This Raid mode can support up to two disk failures with no data loss. RAID 6 provides for faster rebuilding of data from a failed disk.

Applications

RAID 6 provides data reliability with the addition of efficient rebuilding in the case of a failed drive. RAID 6 is therefore useful for people who need serious security with less of an emphasis on performance.

How RAID 6 Capacity Is Calculated

Each disk in a RAID 6 system should have the same capacity.

Storage capacity in a RAID 6 configuration is calculated by subtracting the number of drives by two and multiplying by the disk capacity, or

C = (n-2)*d where:

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

For example, in a RAID 6 array with five drives each with a capacity of 1000GB, the total capacity of the array would be 3000GB:

C = (5-2)*1000

RAID 6

A1

B1

C1

Dp

Disk 1

A2

B2

Cp

Dq

Disk 2

A3

Bp

Cq

D2

Disk 3

Ap

Bq

C3

D3

Disk 4

Aq

B3

C3

D3

Disk 5

Fig. 87