Can't we add some extra fork that stores this extra per-page information, and contains this extra metadata
+1 for this approach. I had observed some painful corruption cases where block storage simply returned stale version of a rage of blocks. This is only possible because checksum is stored on the page itself.
A special fork for checksums would allow us to better detect failures in SSD firmawares, MMU SEUs etc, OS page cache, backup software and storage. It may seems that these kind of stuff never happen. But probability of such failure is drastically bigger than probability of hardware failure being undetected due to CRC16 collision.
Also I'm skeptical about correcting detected errors with the information from checksum. This approach requires very very large checksum. It's much easier to obtain fresh block copy from HA standby.
