I'm really lucky in that I get to work with a lot of very smart and experienced people. So when I encounter something that has us all running fruitlessly to Google, I figure it might be worthwhile to share the knowledge.
Doing a reduced-capacity disaster recovery site is relatively common. Basically, this is a scenario where you have multiple production sites, and while your DR site has all the data from all the sites, there's only enough processing power to run one services for the largest production site. Depending on how many production sites there are, the savings can be considerable.
So we have a customer with 5 production mailbox servers at different sites around the US and a single mailbox server at their DR site. They had all their databases, checkpoint files, and transaction logs, but mounting the database failed, and running eseutil /r failed with the following:
Operation terminated with error -1216 (JET_errAttachedDatabaseMismatch, An outstanding database attachment has been detected at the start or end of recovery, but database is missing or does not match attachment info) after 1.937 seconds.
That was brand new to us. When the guy with 11 years of very deep Exchange experience asks, "what's a 1216 error?" you know you have something interesting. After futzing around with a bunch of different settings, we changed the drive letters to be identical to the production server, and not only did eseutil run properly, we didn't actually have to run it to mount the databases. It should work when the drive letters different, but troubleshooting this is not worth the effort.
