Upgrading From Previous Versions

Upgrading from all 2.4 series to 2.5

      * It is strongly advised to shut down the server completely while
        performing the upgrade, because newer daemons will write
        mailboxes.db entries which aren't compatible with the old daemons,
        and may cause crashes if you try to upgrade a running server. You
        can start the server again immediately with the new daemons
        installed. 
      * The most important change is that index file upgrades are no longer
        automatic. This avoids the IO storm caused by upgrades from 2.3 to
        2.4. Even if you are upgrading from Cyrus 2.2, it won't cause an IO