On Jan 28, 2013, at 1:44 PM, Piergiorgio Sartor [off-list ref] wrote:

It could still be the data is as it was written,
but, for some reasons I could not imagine, the
parities (both) are not correct.

In RAID 6 are the two parity chunks in a stripe identical? If yes, does 'unknown' only tell us that the data chunk recomputed parity does not match either of the parity chunks; or does it tell us anything about whether the parity chunks themselves are still the same or different?

This could be in case of some software bug, which
would be quite a surprise, I must say.

Yes, it sounds reproducible on more than one array, more than one HBA. Is it also more than one computer also, Wolfgang?

I think regression is going to be needed to find it. Hopefully the problem is restricted to parity computation and data chunks aren't affected; however if a URE occurs in a data chunk, it could be reconstructed incorrectly from bad parity so it's obviously still a big problem.

Chris Murphy