Less than that, you could get away with 500GB no problem. For a small server (say 10 slots) you could run a server fully boosted and still get away with it. If you will be running multiple servers you'll want to invest in something with a little better specs.
keep in mind CPU = How man simultaneous Players
and you RAM = How many simultaneous Servers
If you create a server with your HLDC tool, click your Bandwidth tab, and do about an hour of playing. You can get roughly how much bandwidth you will move with simple math.
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