Re: Optional DR/Resiliency
"If you want a backup system, it will cost you what the real system cost, again, and a bit more for whatever tech to make it fall over."
There are different degrees of the extent to which you might need to provide resilience. What you describe is a full-fat failover. However, it might be satisfactory to have a DR contract which is much cheaper - you have access to a system which might actually be bigger than your own on which to restore your backups. If your DC is in your normal premises the time to get the DR contract invoked and running might be of the same order as the time taken to get your staff established in whatever temporary offices they've made provision for. OTOH this wouldn't suit a business which has to be running 24/7. But one size doesn't fit all.