We are building a new Spectrum system with the following:
Site 1: 12.000 routers / switches, 12.000 Pingables
Site 2: 8.000 routers / switches 19.000 Pingables
The Spectrum Sizer Tool recommends:
with WATCHes the sizer calculates 4 servers
without WATCHes the sizer calcukates 2 servers
Release : 21.2
It is difficult to give a recommendation based on just the number of devices as there are many other factors that influence the resources needed.
With the introduction of 64bit Spectrum, the limit per SS is 1 million models (not devices). We document model count and not device count and some devices create many, many more models than others e.g. large switches with a huge interface count. With the introduction of huge landscapes can go as high as 2 million but for these numbers the resources on the server will need to be much especially RAM than what is documented. If all your switches have thousands of interfaces, you will go over the 2 million model count.
The number of models is not as important as the traffic they generate which is what costs the SS and OC servers. e.g. 1 server that is creating traps storms can have a bigger cost to the resources than 1000, that are not.
Also How often are the watches run? This was not considered by the sizer.
The current sizer tool is slightly outdated and a new NetOps sizer tool is currently being developed which takes many more factors into account.