help designing system layout - standalone linux computer

[jaybo]

Hey guys Im gonna jump right in, and I apologize for the long winded explanation!

Ive decided to setup some home security cameras. I've 100% decided to go the route of IP cameras (1-2 for now, while upgrading to 3-4 in the distant future). I've also decided that I don't want a stand alone (preboxed like swann or Q-see or whatever) DVR. I've familiarized myself enough with linux to know that this is the route I want to take.

I'm leaning towards TrendNet TV-IP310PI 3mp cameras as they provide a good value, are compatible with zoneminder, and I can buy them locally (avoiding ebay/amazon issues).

I've currently got a NAS server running linux - I built this for the same/slightly higher cost as buying a stand alone NAS box like a Drobo and for the same reason I don't want a stand alone preboxed DVR. I like having an actual powerful computer running my shit.

Specs;

-Ubuntu 14.04.3 server
-Intel i5-4570 quad core
-16gb ram
-20+ tb over 2 different raid arrays
-SSD running OS
-SAS expander (8 future drives)

This runs plex, which serves bluray/music etc to 4 chromecasts in my house (although no more than 2 at a time).
It also doubles a backup server with a RAID6 array, which archives my Gopro data, family pictures/movies and other backups. I have 20TB on my desktop so I needed a backup that could handle at least 20TB. I'm a packrat when it comes to my data.

In the future I may use this server for other things, like a VM host etc, but for now, this is it.

Now to the meat.

Its my understanding that 2 cameras, running at 2048x1536 res, at 30 fps each, on the H.264 codec, will require about 30.82 Mbps of internal network bandwidth as detailed on a online bandwidth calculator I found


Im not worried about the data storage, I've got millions of hard drives ranging from 200GB to 1TB just lying around.

My main question is this;

a) Should I tax my existing server with the burden of running Zoneminder and sucking 31Mbps constantly (off my Gigabit network mind you)? This would be the cheapest route I know, as I would just run the cameras to a PoE switch which I would just plug into my existing network. Voila!

b) Should I run the cameras on a PoE switch, that connects to a secondary GbE network card on the server, as to eliminate any issues on the main network. That way the cameras feed directly to the server, but the server is still in turn connected to the network and in turn, connected to the internet. I understand this will be a bit of a nightmare config wise with multiple network cards and ip addresses

My secondary question is;

For under $400 I can build a new Intel i3 system in a nice microATX package. Would this be a better option? As I said before, a good stand alone boxed DVR is going to cost me that much or more, and I like the idea that I get an actual computer out of it.

Thoughts? And thank you in advance. I'd really like input on designing my system.

[jaybo]

Upon reading further, I understand that the motion detection is what really cranks the cpu the most (am I wrong?)

I really don't mind recording 2 cameras constantly, although I know that it will be harder to pinpoint security events.

How decent is the motion detection?

Its looking like a second separate server to run the cameras may be what I want due the the amount of data the server will be processing. I really don't to bog my existing server (although I dont use more than 10-20% cpu in its current configuration)