New in PostgreSQL 9.0 is a utility named
pg_upgrade, supplied as a contrib module.
pg_upgrade allows you to migrate to new major versions of PostgreSQL, such as from 8.4 to 9.0, or from 9.0 to 9.1.
In-place upgrades means upgrading your database without moving to a new system. That does sounds good, though
pg_upgrade has a few things that you may wish to consider as potential negatives, which are as follows:
pg_upgrade, or use the recipe on upgrading using replication tools. If you use the link option on
pg_upgrade, then ...