At our company, we currently have 2 7825 CUCMs: 1 as Publisher and 1 as Subscriber. They recently purchased a new 7835 which they plan to replace the 7825 as the Publisher and then use the 7825 as a Subscriber. My question is: Which would be better suited as the Publisher, the 7825 or 7835? Shouldn't the 7835 be used as an active subscriber which would be handling the bulk of the call processing? I checked the SRND, but it doesn't mention anything about this. I'd like to get your opinions!
Thanks very much,
As far as best practice, it is actually best to have the same hardware platform across the cluster. However, this isn't always possible. In your case, you have a 2 server cluster so the Sub is the primary call processing agent and the Pub is likely a backup. No matter where you put the 7835, the scalability of the cluster is limited to the sizing of the 7825 because you always have to consider the failover scenario.
So, if I were you - this is what I would do:
Use the 7835 as the Publisher for now. The size of your cluster is limited to the sizing of the 7825 which will remain as the primary call processing agent (i.e., Subscriber). From there, put a plan in place to upgrade the Subscriber to a 7835 and then you have matching hardware and have, at the same time, boosted the capacity of your cluster.
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My vote would be to use the newest most powerful box as the Publisher. Even
though it does not normally provide "call processing" functions, it is the
most important node in the cluster due to dB -write capability. If there is one
box you don't want to have fail....it's the Publisher.
Just my 2 cents