Re: Help, server doesn't start

  We plan to upgrade to version 9.1, do you know if file result of the pg_dump in 8.3 can be restored in 9.1?

Yes, pg_dump output from 8.3 should restore fine to 9.1. PLEASE READ THE RELEASE NOTES for the intermediate major versions (8.4 and 9.0) for upgrade advice and caveats.

http://www.postgresql.org/docs/current/static/release-8-4.html
http://www.postgresql.org/docs/current/static/release-9-0.html
http://www.postgresql.org/docs/current/static/release-9-1.html

Do not just try to upgrade your production database. Do a test with a test copy first, and test your application against it; don't just assume it'll all work.

--
Craig Ringer