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LaCie RAID Technology White Paper
RAID 3+Spare
In RAID 3+Spare, one disk in the array is left empty. If a drive in the array fails, the data from the failed disk is
automatically rebuilt to the empty or “spare” disk.
Applications
In RAID 3+Spare disk failure does not require
immediate attention because the system re-
builds itself using the hot spare, but the failed
disk should be replaced as soon as possible.
RAID 3+ Spare
Disk 1
Disk 2
Disk 3
Disk 4
A1
A3
B1
B3
C1
C3
A2
A3
B2
B4
C2
C4
Ap(1-2)
Ap(3-4)
Bp(1-2)
Bp(3-4)
Cp(1-2)
Cp(3-4)
Spare
LaCie Products with RAID 3+Space
LaCie 4big quadra
✦
How RAID 3+Space Capacity Is
Calculated
Each disk in a RAID 3+Spare system should
have the same capacity.
Storage capacity in a RAID 3+Spare configu-
ration 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 3+Spare array with four
drives each with a capacity of 1000GB, the to-
tal capacity of the array would be 2000GB:
C = (4-2)*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
