How do I size my Exchange to Office 365 migration?

Here is a very rough breakdown of what speeds you can expect. Note: this is by no means an SLA, but just an example based on a very large sample of migration speeds experienced by us.

  • Low-end: 250MB per hr/per user
  • Mid-end: 750MB per hr/per user
  • High-end: 1.25GB per hr/per user

If you want a predictable timeline of how long your migration will take, we recommend sizing your migration before it happens. This is particularly important for larger migration projects.

Sizing your migration consists of performing a Proof Of Concept (POC) migration ahead of time, and using the statistics generated to extrapolate duration and speed. This POC migration should be performed against a few larger mailboxes.

  1. Perform a POC. This should include the migration of three (3) larger-sized mailboxes. To perform this POC, follow the steps from the migration guide that we will help you create to matches your scenario.  Important: The migration speeds seen during your POC may vary from your actual migration speeds, because many factors, such as available bandwidth and server resources at the time of migration, may be different between migrations.
  2. After the migration completes, we can show you the statistics for the mailbox and make note of the lower data speed (the lower data speed of the Source or Destination). The lower of the two speeds is the rate in which the migration is moving.  In the example in the table below, the lowest migration speeds are at the Source. Therefore, the average mailbox speed will be the average value of the Source speeds. In the example below, this average speed = 600 MB/hr.
​Mailbox Name ​Source speed MB/hr ​Destination speed MB/hr
​mailbox 1 ​500 ​700
​mailbox 2 ​600 ​800
​mailbox 3 ​700 ​900

Once you have completed the steps above, you will have some accurate data to help you determine how long your migration project will take to complete.

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