Because availability of systems is important, we offer cluster services. This allows us to provide you with a load-balanced and/or high-availability solution based on your requirements.
We can integrate this with most, if not all of our solutions.
Depending on the cluster you require, it would generally require a minimum of three servers in total. The reason for this is that you have a virtual server which acts for redirecting the services you are utilising. These services don't exist on the virtual server - the server is just configured to accept that connection before it sends it to a real server. The real servers are where the application/service is running, and so this is why two machines are required in this instance. This is so that if one real server fails, the virtual server will ensure that connections are routed to the remaining server.
For High Availability, this would require additional servers to provide multiple virtual servers providing access to the real servers ensuring no single point of failure. With load balancing, you normally only have one virtual server, and so this would be seen as the single point of failure. By providing multiple virtual servers as well as more real servers you are ensuring that you guarantee your service availability.