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LaCie RAID Technology White Paper
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 the diagram at right) 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 addi-
tion 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.
LaCie Products with RAID 6
LaCie 5big network
✦
RAID 6
Disk 1
Disk 2
Disk 3
Disk 4
Disk 5
Ap
Bq
C3
D3
Aq
B3
C3
D3
A3
Cq
D2
Bp
A2
B2
Dq
Cp
A1
B1
C1
Dp
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 ca-
pacity of the array would be 3000GB:
C = (5-2)*1000
RAID 0
RAID 1
RAID 3
RAID 3+Spare
RAID 5
RAID 5+Spare
RAID 6
RAID 0+1
RAID 10
Concatenation
JBOD
RAID Selection
