Span WordPress over 2 Servers w/ failsafe

Hello,
I’m working with a client who had several WordPress installations on a shared bluehost account, and there were so many issues involved with it, mainly with the database server reaching it’s load (it was only 11 Mbs?!) and we were being throttled because of this. I ended up moving him to a VPS Solution.

He wants met to set up a failsafe, or redudndant solution for his site. I know I can use Round Robin DNS, but that doesn’t help in the case of a server going down because of cached dns paths. What is the best solution for load balancing and redundancy?

Thanks
Zach