In a multi-node computer system, a software version management system is described having a version manager for ensuring that cluster nodes running completely incompatible software are unable to communicate with each other. The version manager provides a mechanism for determining when nodes in the cluster are running incompatible software and providing a way for determining the exact version of software that each node must run. The version manager provides support for rolling upgrades to enable the version management software to ensure the chosen version of software that runs the cluster stays constant even though the software installed on individual nodes is changing.