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Organizations should ask important questions as they weigh the option to migrate to Office 365, including what migration method best suits their needs.
The first two questions help admins decide how to handle domain names, as well as how Office 365 will identify users and groups. Now, it's time to choose which migration method to employ.
There are three ways to migrate to Office 365 from Exchange -- cutover, staged and hybrid approaches. Administrators must understand the scope and issues with each approach before embarking on the big move.
Have you picked a migration method?
Cutover migrations: A cutover migration is a single, massive provisioning and transfer of local Exchange mailboxes, end users, contacts and mail groups to Office 365. The Migration dashboard in the Exchange Admin Center (EAC) typically handles cutovers. This migrates every mailbox in the same process, and there are no subsequent migrations.
A cutover process to migrate to Office 365 can handle up to 2,000 mailboxes and can take several days to execute; it depends on the total number of users, contacts and mail volume. Exchange and Office 365 mailboxes are no longer synchronized once the cutover process is complete because email will flow to Office 365 rather than the local Exchange server, so there is no opportunity to run Exchange and Office 365 in tandem for any period of time.
Staged migrations: The complete commitment required for a cutover is simply not possible for some organizations. Mailboxes can be moved in smaller batches over a much longer period of time using a staged migration, which also occurs through the EAC's Migration dashboard or the Exchange Management Shell.
A series of database files (.csv) defines each batch of user and mailbox data. As with a cutover migration, a staged migration doesn't handle more than 2,000 mailboxes. Migrated end users will still be synchronized with the local Exchange server until the migration is complete, but long-term coexistence isn't the idea. The goal is to move end users to cloud email rather than local email servers.
Hybrid migrations: It's important to note that staged migrations don't work with Exchange 2010 or Exchange 2013. A hybrid migration option through the EAC may help organizations with recent Exchange platforms that need to move more than 2,000 mailboxes, organizations that don't intend to move all users, or organizations that wish to simultaneously run local Exchange servers and Office 365.
A hybrid migration creates user accounts and copies content to Office 365. It also provides a unified shared address book, calendar sharing and the opportunity to move some Office 365 email users back to the local Exchange server again.
This is part three in a checklist about preparing for Office 365 migrations. Part one covers Active Directory and company domains and part two covers options for establishing user accounts.
Stay tuned for part four, which covers migration tools.