I need to upgrade our Unity Connection cluster from version 7.0(2) to a later version (looking at 7.1(3b)SU2). I've noticed that in the "System Requirements for 7.x" under "Cluster Requirements When the Servers Are in Separate Buildings or Sites" it mentions that both servers need to belong to the same platform overlay.
Currently we have two servers in our cluster (located at separate sites), one being a 7845H2 and the other a 7835H2 (Platform overlays 3 and 2 respectively). Does anyone know what issues we should expect to see occur as a result of having two servers in different platform overlay groups?
Our system was installed by a 3rd party, and this is the first time i've had to look into the clustering requirements.
We have had TAC calls open in the past looking into failover issues with our cluster, and none have mentioned this incompatibility, only suggested that an upgrade may help.
Any replies would be appriciated!
I suspect the main reason you're being told you should upgrade is because you're on 7.0 which was riddled with bugs. 7.1(3) and specifically 7.1(3b)SU2 (my recommendation to you) has been very stable. You are correct about the requirements to use the same platform overlay. From a "will it work if I don't" perspective, the answer may likely be no. I've never looked that deeply into the requirement because, personally, I have not installed nor would I recommend a mixed cluster from a hardware perspective. The reasoning being that Unity Connection is intended to provide 100% failover between servers. So, if you have a 7845 and a 7835 then the effective capacity of your cluster is that of a 7835. This means you have to be cognizant of what load is being placed on the servers and that you distribute workload and overall cluster size (e.g., subscribers, ports) such that, in a failover scenario, you don't overload the smaller server. This requirement actually stems back to the original Cisco Unity. Some may not know but, in a Unity failover scenario, you should match the 2 servers in overlay as well. Some of this is due to file replication and such but again some of it is due to server sizing and have equal capabilities between servers during failover. With CUC, the architecture at a high-level is similar to that of CUCM and while you can have a mixed cluster in CUCM (different server types) - best practice recommendation is to use the same platform across the cluster.
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