I have a customer running Unity 4.x on MCS 7835 Single Server with Onbox Storage supporting up to 2000 users.
The customer has already purchased Unity 5.X upgrade with 96 port, and now I am in process of selecting an appropriate hardware. The basic requirements are:
The hardware will need to support up to 5000/6000 users gradually.
Not all of the users would require Unified Messaging. Some would stay with Voice Mail only and some would be upgraded to Unified Messaging.
I am going to recommend 7845-H2 with failover configuration, but need some feedback regarding the appropriate choice between ECS3 and ECS4.