At my last job they had Dell servers running vmware infrastructure.
They had like 6 think rack servers, all running vmware OS.
You could login to the VMware infrastructure client, create any os on any machine, take snapshots, deploy a template, move the image from one server to another... all that in a couple of clicks. Each machine can run several OSes concurrently over a VMware layer.
Sadly, half these servers werent even in use, except for testing and such... (so if u think u or someone could buy one of these, PM me)
I think that would be overkill for your requirements. Just buy el cheapo hardware with a good ups. Buy 3 or 4 samples of the same hardware (so that you have backup and spare). Also get a fast 1tb external USB disk.
Using dd under linux you should be able to backup the whole disk in 1/2 to 1 hour maximum.
If you have similar hardware, if something fails u can just move the harddisk to another machine with the similar hardware (thats why im telling u to get similar hardware). Now if youre running windows I cant guarantee anything, Im not up to date with windows validation and cloning... I know it usually works well with 2000 and XP... thats about it.. for windows server ull have to test and research
If the HD crashes u have a bit-per-bit backup and can restore it through a live CD.
Anyway, that is just my suggestion, based on my experience and my approach.
Whatever u do, like bash said, get a good UPS first.
rahmu wrote"Server machines" are nothing but your average computer without screens, keyborads, mouse, ...
They are engineered and tested for superior reliability, may include technologies such as hot swap and parity protected RAM, normally have a serial interface and an additional Ethernet interface to remotely control it...