Does Postgres database support differential backups
You can do it the "snapshot and archive log" way in postgresql 8.4. See section 24.3 in http://www.postgresql.org/docs/8.4/static/backup.html
You have to take off the database on the initial backup.
Something recently mentioned on the pg-admin list - "pg-rman (PostgreSQL Recovery Manager)".
pg_rman is also a tool. However this tool is not available for Windows. Suggested is to use pg_dump/pg_dumpall or Filesystem Backup. For more information, please follow the link given below: http://www.postgresql.org/docs/8.4/interactive/backup.html
Regards, Vibhor Kumar.