You must upgrade the storage server first, then upgrade application servers.
You must upgrade all application servers and storage server to the same release of Messaging software.
If you are upgrading clustered environment, before you upgrade Messaging, you must remove all the application servers from the cluster and mark all the application servers as Inactive. After upgrading Messaging, add all the application servers that you joined into a cluster to the individual cluster lists of the servers and mark the servers as Active. For more information, see Administering Avaya Aura® Messaging.