Delayed Parity in RAID 5
Some controllers, like HP SmartArray, use nonstandard scheme of striping called delayed parity.
Effectively, two different block sizes are used, one for parity and the other for the data.
A parity block size is an integral multiple of data block size.
Thus, two additional parameters appear in the RAID configuration - delay and firstdelay.
Delay parameter indicates multiplicity, namely how many data blocks fit into one parity block;
firstdelay shows how many data blocks are contained in the first parity block.
The possible delay values are 1, 2, 4, 8, 16, 32, and firstdelay can be from 1 to delay value.
If both parameters are equal to 1 then we get a usual RAID 5 array with no delay.
Recover array with delayed parity
ReclaiMe Free RAID Recovery, starting with build 301, automatically detects and recovers arrays utilizing delayed parity.
It will produce correct output if you write array either to an image file or directly to the disk.
Also, it will transfer the parameters to our ReclaiMe data recovery software,
starting with ReclaiMe build 1103.
The transfer instructions for other data recovery software cannot be produced as of this writing (with build 306).
The generation of these instructions is expected to be updated soon.
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