High core speed, intel, thats it. Fast Quad Cores seem to perform really good, Intel Six/Octacores can be somewhat better.
A fast SSD will only help you with loading speed/improve your database speed, ram can improve some parts but will only change much if you store the whole server (or db) in a ramdisk.
Depending on the amount of players you should atleast have a 100Mbit connection, 1gbit would be even better.
Most important (in order of appearence) are definitely CPU - RAM - Hard Drive - Graphics Card (Server and Client). Why? Arma 3 is a very CPU based game, no question. Moreover the RAM is also needed, especially for caching and all those stuff blah... Also very much textures (= pictures in this case) and faces (... or simply said: many models) are loaded in a short time - so a good SSD is definitely better than an old HDD and an important fact not to forget (good SSDs start at ~60€ and have anough space for Arma 3 + some Mods). The Graphics Card is.... yeah... kind of unnecessary. Why? Arma 3 has as much graphic calculations than Photoshop. Why? In Photoshop you actually draw lines etc which have to be calculated (mostly by CPU there as well, but nevertheless...) - Textures in Arma 3 are just pictures, the engine put on a model and tells you it has painted it. It didn't. That's simply why you can play Arma 3 even without graphic card...
Hope I could help you understand this logic a bit 
Good Setup for server is definitely:
Arma 3 without a beafy gpu ?
@Edwin That server configuration is pretty good, you shouldnt run into trouble hosting a well scripted Life Mission with some mods at 60-80 Players on that.
ProcessorCores/ThreadsFrequencyRAMDisksCarte réseauBandwidthTrafficIPv4IPv6
Intel i7 4790K 4 cores/ 8 threads 4 GHz+ 16 GB DDR3 1333 MHz 120 GB SSD - Samsung EVO 840 1 Gbps 250 Mbps Unlimited 1 /64 It's good ?
Yeah.... Well... For a PC is it not bad, but a server? Someone tricked you. Never rent a server with a Desktop CPU. XEON processors were developed on purpose, because they can perform better on servers even with less frequency, because they lack the graphic unit, wich restricts the Desktop CPUs in their effectiveness on servers a lot. 120GB of SSD is fine, but for me it would be full in no time xD everything else is OK, 16 GB DDR3 is enough as well as the conection
Arma 3 without a beafy gpu ?
You don't need a GPU... I tested it for fun: unplugged my GTX 960 and just used my integrated HD graphic (actually not sure if the one from the CPU or the motherboard, but that's not important...). I was kinda surprised when I realized, that was only a lack of FPS that is not really noticeable - like 5FPS and they could have been caused by other factors as well. So: Arma 3 doesn't really need GPU.
BUT: If you don't use a GPU, you will need more RAM for caching the textures etc
Okay okay, what are you actually talking about, have you set up arma 3 servers and tested Xeon CPU and Desktop CPUs ?
On what kind of settings did you test that ?
Xeons are simply i7 CPUs, using the same architecture just without the onboard gpu
I tested on i7 as well (on a friends server) and for me it did not reach the same CPS with same configs etc, but it's actually not that bad and definitely ok, sorry if it sounded like it's a no-go
tested on Custom Settings (Very High-Ultra, just my normal Setup) on Arma 3 1.54
"tested" Tell me more about that test, you used the Server in a production environment, with real players, mods and a heavy mission ?
heavy mission under load of ~20 players, same settings and normal gameplay. i7 had more instabilities in CPS compared to XEON, and most hosters don't even use i7 for their solutions btw...
Definitely. Unstable, hard to manage the server (you can't set startup parameters directly), no BEC or alternatives and it's lacking the user interface, which can be very helpful
Dont go for Arma 3 with Linux. Linux and Arma 3 dont like each other. Go for a Windows Server.
I Prefer this Setup for an Arma 3 Server:
Core I7 with 4+ GHz
32GB Ram (Arma 3 only can Handle maximum 4GB but you can use a Ramdisk for Database)
2 x 128 GB SSD in Raid 1 (One SSD can Crash and you have all youre Data Save)
1Gbit/s
With best regards from Germany. Sorry for my Bad Englisch
We are running a i7 5820k (4.2ghz), 128 gb ram, with 80 players, a huge modpack and heavy mission, we see no "instabilities" in cps
