We have customers with not quite TB levels, but at least several hundreds GB databases. Upgrading the database server is as simple as shutting down the service

We have customers with not quite TB levels, but at least several hundreds GB databases. Upgrading the database server is as simple as shutting down the service, installing new executables and restarting the service. Downtime is measured in minutes. When upgrading major versions, one might not get full functionality of the new features unless one upgrades the on-disk format (unload-reload), but you can run the new server version with older on-disk format just fine.