Let's say we have three drives, two groups of three disks. Each three disks form a RAID5, and there are two of them, left side and right side. Each RAID5 has three columns.
Code: Select all
left - right
A B C - D E F
1 2 P - 3 4 P
5 P 6 - 7 P 8
P 9 10 - P 11 12
where A B C D E F denote disks, P is parity
Disks A and D are in the first column of their side RAID5 (and both have parity in the bottom row). In a similar way, B-E are in the second column, and C-F are in the third column of their respective sides. Entropy analysis gives you that pairing. You just do not know which drive is from which side.