We have used Webanywhere for about three years now and I believe we were the first school they installed a Moodle Server into which they managed totally remotely (because I insisted on it so that if the internet failed we could still teach). When we migrated to Moodle 2.0 last summer they did the whole thing remotely and it has been running well until now. They use a software raid and a management server (virtual) to access the Virtual Moodle Server so they are responsible for all backups and disaster recovery. The guy who set this up originally was Anthony Wright who runs a company called Overnet Data Overnet Data - Moodle / MIS Integration Specialists who now provided Moodle support and SIMS integration.
Webanywhere are not a cheap solution because they have grown fast and have a large support team. Overnet data may provide a cheaper quote but I know that this chap is brilliant with Linux and really knows what he is doing.
I played with Windows Moodle but it kept crashing so decided to stick with Webanywhere for now so I did not have the worry of things going wrong.
I am now looking at load balancing because I am not happy that when the server needs fixing it can take more than a day for it to be sorted (usual remote support problems- engineer not available, delays from them and me being able to spend time on it etc etc). Ideally I would want two Moodle servers with failover to the second one should the main server fail. Our teachers rely on this for their day to day teaching and the Moodle Server is available directly from the internet.
If you want to try out our Virtual Loadbalancer please drop me a PM
The issue you have is not uncommon. Load balancing Apache is easy enough to do, the issue comes with the database. If you have 2 servers, they both need to be able to read the database, and both need to be able to write to it.
From what I've seen, Moodle doesn't play that nicely with NDB, so you'd want to use a master/master setup - with a copy of the database on both servers, and each replicating to each other.