Unable to change database path on Exchange 2010 in a DAG?
If you find yourself unable to change the database path of an Exchange 2010 database, check whether it is part of a DAG. See the screenshot for the missing option:
If so, you cannot move it. The solution is to remove all copies except the active. Now you can move the DB and Transaction log paths.
Do note that you will have downtime! Changing the path requires a dismount and since you do not have the redundancy of a DAG, you will have to plan this in a service window.
After you are finished, you can add Mailbox Copies. Be sure you have made the same drive changes to the other DAG members!
Databases within a DAG need to be on the same drive letters and same unique path. It is tricky to change the location of the DB when you have to consider 15 other servers (DAG member maximum). The same drive configuration has to be present.
Of course it is better to have the database locations correct right from the start, but unfortunately we don’t live in an ideal world. 
I'm an employee at a Dutch IT-Company (www.ogd.nl) and frequently come in contact with customers with specific questions on Microsoft products. Of those products my personal favorite is Microsoft Exchange.
Sander made me aware of the DirTeam.com/ActiveDir.org blogs.