Hi
One new question from me: how about replication?
Case: primary+replica, we shut down primary and enable checksum, and "started streaming WAL from primary" without any issue. I have master with checksums, but replica without.
Or cluster with checksums, then disable checksums on primary, but standby think we have checksums.
Also we support ./configure --with-blocksize=(not equals 8)? make check on HEAD fails for me. If we support this - i think we need recheck BLCKSZ between compiled pg_checksum and used in PGDATA
regards, Sergei