The most common problem with RAID5 is...

... that one does a rebuild with the wrong order of disks.

This is by far the most common scenario we at have for an unrecoverable RAID 5. Something bad happens and the configuration is lost. The operator then assembles the array in a way which looks correct, and does a rebuild on it. The configuration which looks correct is just not good enough. You need a configuration which actually is correct.

Doing a rebuild on a RAID 5 with wrong block size or disk order effectively destroys the data on the array. Theoretically, the data can still be restored, but practically the complexity of having two sets of parameters (with unknown block sizes, disk orders, and such) precludes any recovery.


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