A generally accepted best practice for migrations is to create several test user accounts and use them to conduct systems tests. After you have successfully moved and tested those accounts, you should identify a group of pilot production users and move their accounts and conduct validation tests on them. If the results are satisfactory, you can move the rest of your users to the new deployment.

Consider your compliance requirements before you move user accounts. Office Communications Server 2007, Archiving Server, cannot archive traffic from users who are homed on an Office Communications Server R2 pool. If you have compliance requirements, you will have to deploy the new Archiving Server before you move users to the new pool.

After you have established a new Office Communications Server 2007 R2 pool, plan and execute your Edge Server and Director migration. Office Communications Server 2007 edge server roles will support an Office Communications Server 2007 R2 pool; however, you should consider how you will deploy Office Communications Server 2007 R2, Edge Server, before you move active users to the new pool. Because you will still need the existing edge servers while you deploy the new ones, you must create new DNS entries and firewall routing in order to have both versions active at the same time. This coexistence may affect the experience of external and remote users, and it may also affect the timing of your user migration.