Just as in Operations Manager 2007, OpsMgr 2012 does not prevent an OpsMgr administrator from placing management servers into maintenance mode.
The Problem with OpsMgr 2007 Management Servers and Maintenance Mode
A common problem in OpsMgr 2007 was that when a management server was placed into maintenance mode, it would never exit maintenance mode. In particular, placing the root management server (RMS) into maintenance mode would literally stop monitoring in the management group altogether. This led to scripts and utilities to monitor for all OpsMgr 2007 management servers being placed in maintenance mode at the same time. In OpsMgr 2007, the root management server could not take itself out of maintenance mode as maintenance mode unloads all workflows, which included the Maintenance Mode workflow itself (which as an OpsMgr rule calling a maintenance mode SQL stored procedure).
What’s Changed in Maintenance Mode in OpsMgr 2012?
Fortunately, the new resource pool feature of OpsMgr 2012 opened the door to change the way management server management mode works. In Operations Manager 2012 the Maintenance Mode workflow is targeted to the “All Management Servers resource pool” instead of the root management server class (see image below).
Specifically, if a management server is placed into maintenance mode, then the System Center Management Configuration Service (aka ConfigSvc) will shift workflows targeting the All Management Servers resource pool to another management server. This means the Maintenance Mode workflow continues to run and so the management server can be removed from maintenance mode according to the time configured maintenance mode duration.
The only way you can screw this up…
This failsafe is nice, but there are two ways you can still screw this up:
If you only have one management server and you place it into maintenance mode there is no failover capability. A resource pool of one is not worth much.
The other would be if you placed all management servers in the “All Management Servers resource pool”.
With a little forethought, the maintenance mode challenges of OpsMgr 2007 are history thanks to the topology improvements in OpsMgr 2012!