A method and apparatus for ensuring high availability of services in a communication server. In particular the invention relates to a method and apparatus for ensuring high availability of services in a software based contact centre. The invention is based on a developed application of virtual backup units for ensuring availability in a software based contact centre. The software based contact centre will have a high availability controller, which will have logical connections to virtual backup units on the same server, or different, even distributed servers. The virtual backup unit will typically contain a set of resources that could potentially fail. Once a failure of a resource takes place, a virtual backup unit may be initialised at any server, and some or all parts of the virtual backup unit are arranged to replace the failed resource.