Integration Is Not That Great Between Batch And Individual Mailbox Migration Tools

I was migrating a small batch of some 30 mailboxes from on-premise to Exchange Online in a hybrid configuration. I chose the option to suspend the migration, then complete it manually later.

While most mailboxes reached the AutoSuspended status, some have not even started to migrate (PercentComplete = 0). These few mailboxes appeared to be infinitely looping through statuses like TransientFailureSource, LoadingMessages, InitializingMove and the like:

I said to myself, I couldn't let these "transient" failures and apparent delays hold up the rest of the pack. Experience shows that re-migrating them from scratch usually gets them through.

I was thinking that at the end of the day a batch migration is just a bunch of  mailbox moves treated as one unit, and I should be able to manage individual move requests within the batch via *-MoveRequest commands. I went ahead and finalised the AutoSuspended moves with Resume-MoveRequest. Little did I know that I was about to upset the batch migration logic to the point where it could not recover, resulting in all mailbox moves being reported as "Failed".

To recap:
1. Most mailboxes in the batch finished initial sync and entered the AutoSuspended state.
2. Some mailboxes failed to sync, quoting transient failures and looping indefinitely through various states, never reaching the AutoSuspended state.
3. Using Resume-MoveRequest in remote PowerShell, I completed the AutoSuspended moves.
4. Using PowerShell, confirmed that all resumed migrations have reached the Completed status:

At this point I stopped the batch, removed the failing mailboxes, and restarted the batch. Then I chose "Complete the migration" in the action pane.

I was expecting that the batch will realise that the mailbox moved have been completed and will finish successfully. Well, good luck with that... All mailboxes that have completes successfully following Resume-MoveRequest, were reported as Failed in the GUI. Yes, Failed.

I checked individual reports. They confirmed that the mailboxes were indeed successfully migrated - and please note, these reports were returned by the GUI's very own Download the report for this user link:

The Migration Batch GUI report however showed them all as Failed:

Get-MigrationBatch seemed to be supporting its GUI sibling, returning a status of CompletedWithErrors:

An educated guess indicates that the batch migration wizard is retrieving the report from individual Get-MoveRequestStatistics -IncludeReport commands.

So should I be worried? In my experience, definitely not. Confirmed with users that the above discrepancy didn't affect their ability to connect to and use their migrated mailbox.

Takeaway: Integration between *-MigrationBatch and *-MoveRequest commands (and their siblings) isn't that great. Expect inconsistent reports when mixing them. If you started moving mailboxes using one tool then use the same tool until the migration is complete - don't mix them, no matter how tempting it may be. The inconsistent reports can be misleading but data integrity is maintained. The reports to rely on are those created by *-MoveRequest and *-MoveRequestStatistics. If these commands say that the move has been completed successfully then they have been completed successfully, regardless what other reports say.

Hope that one day Microsoft will improve reporting and integrate batch and individual mailbox migration tools better.

Happy reporting :-)