> So a parity rebuild does so by reading all the data and the > exiting parity, computing the new parity, and then comparing the > existing parity with the new parity. If they match, it's on to the > next stripe. If they differ, the new parity is written out. Oops. What's the point of not simply writing out the computed parity?
> What we don't know here is what the state of the array was when you > started the rebuild. That is, was the parity 'mostly correct' > beforehand? (i.e. saving having to do a lot of the writes). I don't know either. If the discs contained a clean RAID set with a different SPSU, was the parity correct?
