How do I size my migration?
As mentioned in KB004686, it can be difficult to accurately predict how long a migration will take, due to several factors, such as system load, bandwidth, average item size, and Source or Destination bottlenecks.
However, 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 our Partners.
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.
To size your migration, perform the following steps:
Mailbox NameSource speed MB/hrDestination speed MB/hrmailbox 1500700mailbox 2600800mailbox 3700900
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.
To help you understand how to predict this, here is an example project:
Source: On-Premises Exchange 2010
Destination: Office 365
Average mailbox size: 3GB
Number of mailboxes: 500
Preparation steps: Admin account created on Source, and throttling disabled against this account
Migration strategy: pre-stage strategy
Pre-Stage time for completion:
Each mailbox should take 5.4 hours to complete. 100 get completed in the first 5.4 hours. Then another 100, and so on. Remember that when the first one completes, then the next is started so they don't all wait until all others in the 100 batch have completed. However, to try to estimate:
Therefore 5.4 x 5 = 27
27 hours / 24 hours = 1.125 days for Pre-Stage to complete, if leaving migrations going on all 24 hours (some Partners like to run migrations only at night so as not to overload the server).
0.3GB left per mailbox.
Full/Delta Migration calculation:
Therefore at 500mb per hour per user, each mailbox will complete in 36 minutes. First 100 in 36 minutes. Multiply by 5 to get 500 mailboxes migrated = 180 mins. 180/60 = 3 hours for Delta/Full pass to complete.
We highly recommend that you allow extra time for your Pre-Stage Migration pass to complete. Therefore, in this scenario, we recommend that you start the Pre-Stage at least one week prior to MX record cutover.
We also recommend that you create your MigrationWiz project, set the Advanced Options and import users into the project early (at least two weeks prior to MX record) and then run Verify Credentials and Trial Migrations (these do not require licenses). If these succeed, you can be very confident that your Pre-Stage and subsequent Full migration (post-MX record cutover) will work.