Undisclosed, Genetec can achieve your goals, as I understand them from this thread. Genetec offers redundant recording of cameras to multiple locations, archiving failover (consistent within your second post, first item), Directory failover (consider that the main system database), and even some load balancing. With their auxiliary archiving capability you can save separate video streams from the same camera to different locations (e.g. Record one stream at high resolution and frame rate locally and record a second stream to a separate, offsite location at a lower frame rate and resolution).
I am an integrator and have designed and implemented Genetec systems with all of the aforementioned capabilities. We have been very pleased with all the features built into the system. We can use standard servers and don't have to implement expensive, third-party failover and high-availability software packages like Legato or NEC ExpressCluster. You will pay more for Genetec software than Exacq, but Genetec is a better fit for your application and requirements (as far as I can tell from your descriptions). There are also many more cost factors than the software that you should consider in your analysis (server requirements, maintenance, training, etc.).
Note 1: We have also implemented Exacq systems work extremely well, but don't have the capabilities and protections you desire. I am a fan of Exacq...applied to the right application.
Note 2: We have also implemented quite a few Pivot3 systems. They excel in centralized architectures, but don't fit your distributed application quite so well.
As others have mentioned, careful architecture planning is a must! I wish you luck.