On 2019-03-19 13:00:50 -0700, Andres Freund wrote: > As it stands, the logic seems to give more false confidence than > anything else.
To demonstrate that I ran a loop that verified that a) a normal backend query using the tale detects the corruption b) pg_basebackup doesn't. i=0; while true; do i=$(($i+1)); echo attempt $i; dd if=/dev/urandom of=/srv/dev/pgdev-dev/base/13390/16384 bs=8192 count=1 conv=notrunc 2>/dev/null; psql -X -c 'SELECT * FROM corruptme;' 2>/dev/null && break; ~/build/postgres/dev-assert/vpath/src/bin/pg_basebackup/pg_basebackup -X fetch -F t -D - -c fast > /dev/null || break; done (excuse the crappy one-off sh) had, during ~12k iterations, always detected the corruption in the backend, and never via pg_basebackup. Given the likely LSNs in a cluster, that's not too surprising. Greetings, Andres Freund