RAID 6 Recovery
RAID 6 parameters
RAID 6 layout utilizes two different parity functions which helps a RAID 6 array survive up to double disk failure.
Despite of the fact that RAID6 is perceived to be more reliable than a RAID 5, the probability of a controller failure is the same.
So if your RAID6 fails, this will most likely be due to a controller failure.
To recover a RAID6 from a controller failure, you need to know or recover the following parameters:
- number of member disks,
- disk order and which disk was the first in the array,
- block size,
- start offset on the member disks,
- positions of each parity function,
- rotation of parity functions,
- algorithm used to calculate the second parity function,
- pattern of parity functions.
You should know all these parameters to reconstuct RAID 6 successfully.
Our software ReclaiMe Free RAID Recovery (download)
can recover RAID6 configuration automatically.
See the step-by-step RAID Recovery instructions.
RAID 6 variations
RAID 6 is significantly more complex than RAID 5.
The first parity function (XOR, denoted as P on the diagrams) naturally comes from RAID5.
However, there is no widely accepted standard for the second parity function (Q).
Typically, a Reed-Solomon code or some variation thereof is used.
Reed-Solomon code depends on the order in which input is provided.
This produces four more variations: left-to-right or right-to-left and if P or Q is calculated first.
There are several variations of layout accomodating two parity functions.
Missing disk limitations
Although RAID 6 should be recoverable with one or two disks missing, the implementation of ReclaiMe Free RAID Recovery
cannot work with RAID6 having missing disks.
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