pg_upgrade with --hard-link option will upgrade the db in mins, I've done a 2TB db in less than a minute. Yes, there is no rollback, but if you do enough testin

pg_upgrade with --hard-link option will upgrade the db in mins, I've done a 2TB db in less than a minute. Yes, there is no rollback, but if you do enough testing prior it can be really smooth. Am in the middle of doing this across an environment where we have tens of hosts from a few GB to couple TB.