In order to give you time to examine the new installation before archiving starts, you may want to disable archiving and expiry before you upgrade the servers. You can then enable them again when you have checked installation.

In the case of Exchange Server archiving, note that the first run of the archiving service will update archived items to match changes to shortcuts and retention categories. This may take a significant time, so you may prefer to plan for the first archiving run to take longer than normal.

See "Moved shortcuts and changed retention categories" in the ReadMeFirst file.