My tuppence (which is unhelpful in this instance, after the event) I never recommend more than 64 cameras on any box (NVR or server).
They tend to perform badly.
You're asking a lot.
So many cameras.
And then, typically, if you have a lot of cameras you will also have a lot of users.
Multiple connections/viewers.
Loads of streams.
Recording.
Viewing.
Playing back.
Searching.
High-res.
Complex CODECs.
Too much data.
Too much bandwidth.
It's too much to ask.
Inevitably disappoints and frustrates.
I just advise people to avoid, and hopefully avoid disappointment.