I think that if you totally block access to the server until you compleate the maintenence. I mean, allowing access to a broken server under maintenece must just add more strain.
Think of it like this. There is a very busy road used by many many people, there is lots of roadworks around, but still they allow traffic to pass over the roadworks.
You servers are like this, you are doing lots of maintenence on the servers but yet you still leave them live.
I think if you blocked all access to the servers until the maintenence was over there would be much less hastle for the Staff, The Servers and the support board.
Please do consider this,