CCTV Network

Digital CCTV vs Analogue CCTV - Chris Lewis Fire & Security

Redundancy is the only solution, but that also requires redundant power source (UPS works for this).

If you have a single camera, that is no different then a single network. So you need to make the whole system dual, with no common mode fault connection between them.

At least that's what you would do for a system that needed to have essential integrity/availability.

Critical systems have triple redundant implementations.

But your problem exists with any resolution, so why is higher resolution an issue?

Backup in the name of the game .... Murphy's law, if something might fail, it will!
On camera use, I normally combine a wide angle camera set up and a closeup camera looking at the same scene to catch hi res heads, number plates etc. With cameras being so cheap, even the tracking and self zoom systems, then these are other options.
I also have cameras with built in SD card record systems .... how far do you want to go?

I would agree with the local storage of data in the camera, as long as the observed miscreants are not themslves able to get at the camera. Otherwise I see the solution as a recorder for each camera sensor placed at the other end of a short wire.

Here is one CCTV with inbuilt DVR recording solid state to a SD card ... and then connected to a network etc (by cable or wireless link) and the main DVR.

With the cost of these units so relatively low, use 2 cameras at the same location ... one secret (covert) and the other obvious (overt).

may be you can add private and secure wireless fidelity for your digital CCTV to make sure the network doesn't go down.