Over the next two months we will be upgrading from Exchange 2007 to Exchange 2010. We have about 600 mailboxes and a single edb file that is 120GB. What is best practice for size of edb files? Should I split this into several smaller database files during the upgrade process? How many? Should I split it alphabetically, for example A-M and N-Z? We run two servers, a hub transport/mailbox server and a client access sever.