> A disk-block CRC would detect partially written blocks (ie, power drops > after disk has written M of the N sectors in a block). The disk's own > checks will NOT consider this condition a failure. But physical log recovery will rewrite every page that was changed after last checkpoint, thus this is not an issue anymore. > I'm not convinced > that WAL will reliably detect it either (Vadim?). Certainly WAL will > not help for corruption caused by external agents, away from any updates > that are actually being performed/logged. The external agent (if malvolent) could write a correct CRC anyway. If on the other hand the agent writes complete garbage, vacuum will notice. Andreas