If you are migrating from SBS 2008 with Exchange Server 2007 to Exchange Server 2013 or you are migrating from SBS 2011 with Exchange Server 2010 to Exchange Server 2016 the actual migration of the Mailboxes from the old server to the new server cause a tremendous amount of log files created if circular logging is disabled on the new server. This can cause drives to fill up and Exchange to stop working completely and if the database and log files are located on a System drive that can even lead to a non-bootable situation. It is best practice to always move the Database and Log files to a separate partition or drive as explained in How to move Exchange Server 2016 or 2013 mailbox database and logs to another drive.
Enabling circular logging on the new server can improve performance a bit during your migration so let us have a look at how we change that setting. If you have enough free space you can also keep circular logging disabled but you will need an Exchange-aware backup program that can flush logs after a backup has been made. A very good read on Exchange and backup is here Everything You Need to Know About Exchange Backups* – Part 1 – You Had Me At EHLO…