I would've thought I already knew this answer. Maybe I'm just being paranoid.
I have a need to run a local script on a CAS server that would in turn utilize the Active Directory cmdlets. I need to install the RSAT tools for AD (rsat-adds) in order to accomplish this.
In the past versions of Exchange I always put these tools on the servers, but I can't find anything saying whether I should or shouldn't on an Exchange 2013 CAS. I know it is a pre-req for Exchange to function to prep the domain so in the past I've installed it on the Exchange 2010 servers to prep the domain, but wasn't sure if something changed in Exchange 2013 where it was recommended to not install it on a CAS sever.
I have the RSAT tools on our mailbox servers, but not on our CAS servers currently.
So, can I install the RSAT tools for AD on an Exchange 2013 CAS with no concerns?
Having RSAT on an Exchange Server causes no issues.
Providing services like Exchange are mostly constrained to high uptimes and avoiding uneccessary reboots. So, having the RSAT Tools (or other non-vital components) installed, may be related to additional udpates that have to be installed - this may cause the need for additional reboots.
Having a bunch of Exchange Servers (for move server roles) or maintenance windows may reduce the penalty associated with reboots.
A notice on multi-host-scenario: Users working in online mode with exchange may experience some sort of short disconnects even if you manually move active server databases to other hosts. We saw quite often here, that working copies of edited messages have gotten corrupt then and the users had to go back to the stored version of the message from drafts.