I've been using Fusion for years but I've never really know how cores are handled. If I'm not doing anything on the guest system that requires multi-cores then obviously one core assigned to guest OS is fine. So does a i5 system (two cores) have one core going to the server and one to the guest?
If I want to run two guest OS running databases and simple processes am I good to still use a 2 core server or should I be getting and i7 so everyone can have their own core from the quad core server?
I've been running Fusion for about a year in a product environment with Server 2008 running vendor specific software against the wishes of the vendor. Never had to reboot the guest once in 4 months of operation...runs perfect so screw them! So now I want to run two guests and am wondering how the two core (i5) mac mini I have will do with this (16gb of RAM).
Welcome to the Community - remember Fusion is nothing more than application running on top of OSX - so it is the operating system that schedules Fusion - all Fusion can do is request processor time on a specific CPU from the OS - so the OS will use all cores - each VM vCPU can only run on a single at a time - that is a simple explanation on how CPU scheduling works -
Now on to your question if the load is not high from the VMs than yes you should be able to run two vms concurrently.
For OSX guests, always used at least 2 cores. Otherwise, each VM needs to have at most N-1 (where N is the cores in the host server). I can run 4-5 1-2 core VM's on my 4-Core host without an issue.