Geographically dispersed cluster of web application servers on virtualization platforms

For business critical web applications high availability is of paramount importance and clusters of application servers are a viable solution. To achieve even higher availability cluster nodes should be geographically dispersed, i.e. deployed at multiple sites in two or more datacenter premises of a larger business system. In this paper solutions for geographically dispersed clusters of application servers installed on virtualization platforms are described. Most of the time geographically dispersed clusters are overprovisioned and as such are very expensive, considering cost of servers, network, maintenance and software licensing. Virtualization and the choice of appropriate solution can reduce this cost. Advantages and disadvantages of particular solutions are analyzed.