ExchangePro: Only 2 users migrate simultaneously (4311943)

Issue

Actual user mailbox migrations are performed by the Exchange MRS (Mailbox Replication Service). The MRS will only perform the number of simultaneous migrations it is configured to do in the MSExchangeMailboxReplication.exe.config file in the Exchange install folder on the Exchange CAS server.  Microsoft states that the default concurrency is set to 5 migrations.  However, when Exchange 2010 SP1 is installed, it modifies the MSExchangeMailboxReplication.exe.config file to limit simultaneous migrations to 2 instead of 5.

Solution

This value can be adjusted to whatever is needed for your environment.  To do so, open the MSExchangeMailboxReplication.exe.config file on each CAS server and modify the following values to suit your needs:

    MaxActiveMovesPerSourceMDB = "10"
    MaxActiveMovesPerTargetMDB = "10"
    MaxActiveMovesPerSourceServer = "10"
    MaxActiveMovesPerTargetServer = "10"
    MaxTotalMovesPerMRS = "100"

The above values are not intended to be a suggestion for what values to set, but simply a demonstration of which lines in the MSExchangeMailboxReplication.exe.config file control migration concurrency.

In order to configure this within Exchange Pro you can proceed to Settings > Mailboxes and alter the Max Submits, Max Resumes, Batch Submits, etc.