How to verify that postgres 9.3 db has no corruption?
If you have initialized your cluster with checksum, you can control this while backuping with pg_backrest.


  PostgreSQL has supported page-level checksums since 9.3. If page checksums are enabled pgBackRest will validate the checksums for every file that is copied during a backup. 


You will find more information about cheksums here: https://www.postgresql.org/docs/current/static/app-initdb.html#APP-INITDB-DATA-CHECKSUMS

You can also make a pg_dump to /dev/null (if you don't have enough space to keep a logical dump). This should ensure you that you can read each data block.

PGDG had a discussion this year beacuse some wanted to activate checksum by default. You can find it there: http://www.postgresql-archive.org/Checksums-by-default-td5940158.html