* Simon Riggs <si...@2ndquadrant.com> [091130 16:28]: > > You've written that as if you are spotting a problem. It sounds to me > that this is exactly the situation we would like to detect and this is a > perfect way of doing that. > > What do you see is the purpose here apart from spotting corruptions? > > Do we think error rates are so low we can recover the corruption by > doing something clever with the CRC? I envisage most corruptions as > being unrecoverable except from backup/WAL/replicated servers. > > It's been a long day, so perhaps I've misunderstood.
No, I believe the torn-page problem is exactly the thing that made the checksum talks stall out last time... The torn page isn't currently a problem on only-hint-bit-dirty writes, because if you get half-old/half-new, the only changes is the hint bit - no big loss, the data is still the same. But, with a form of check-sums, when you read it it next time, is it corrupt? According to the check-sum, yes, but in reality, the *data* is still valid, just that the check sum is/isn't correctly matching the half-changed hint bits... And then many not-so-really-attractive workarounds where thrown around, with nothing nice falling into place... a. -- Aidan Van Dyk Create like a god, ai...@highrise.ca command like a king, http://www.highrise.ca/ work like a slave.
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