> > The problem I hope to protect against with this approach: the > > CREATE DATABASE might untaint corrupted data from a bad disk > > block into a good disk block virtue of doing a file level > > copy. > > > > I hope my reasoning isn't going astray. > > As I understand it checksums are done on the page level using a hash(for > details: https://doxygen.postgresql.org/checksum__impl_8h_source.html). > I am not sure how a page could get un-corrupted by virtue of a file copy. Ah, no, I did not explain myself well. Let's assume a corrupted, bad (but readable at the hardware level) disk block B. A filesystem level copy (as in CREATE DATABASE) would successfully read that disk block B and copy the corrupted content into a good disk block G elsewhere on the disk. Verifying the checksum of the page sitting on block B before doing the database cloning would reveal the corruption before it got cloned. Does that make sense ? Karsten
