LaCie 5big Network
RAID and Disks
User Manual
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 multi-
plying 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 capac-
ity of 1000GB, the total capacity of the array would be 2000GB:
C = (4*1000)/2
RAID 1
RAID 1
RAID 0
A2
A4
A6
A8
RAID 10
A2
A6
A8
A4
A1
A3
A7
A5
A1
A3
A5
A7
Disk 1
Disk 2
Disk 3
Disk 4
Fig. 88
