Data Redundancy - Nested RAID

Nested RAID is basically combining different RAID level together. I will briefly give 3 example, RAID 01 (RAID 0 + 1), RAID 10 (RAID 1 + 0) and RAID 50 (RAID 5 + 0).


RAID 01
RAID is basically mirroring two or more stripe volumes together, each stripe can contains 2 or more disk. Below show an example of 8 disk in RAID 10.

RAID 10
RAID 10 is basically striping multiple (2 or more) mirrors together. Mirror can have more than 2 disk. Below show an example of 8 disk in RAID 10.

If you have noticed, RAID 01 and RAID 10 are actually very similar. The above 2 RAID 01 and RAID 10 will give the same amount of usable space for data, but the main difference is fault tolerance. RAID 10 provides better fault tolerance. For example if Disk 1 fails, the probability that RAID 10 fails is 1/7, if disk 2 fails. But for RAID 01, the probability is 4/7, if either disk 5 6 7 8 fails, it will fail entirely.

RAID 50

In RAID 50, we are basically striping multiple RAID 5 volumes together.