=>The big difference is that a cluster is homogenous while grids are heterogeneous.
=>The computers that are part of a grid can run different operating systems and have different hardware whereas the clustercomputers all have the same hardware and OS.
=>Another difference. In case of Cluster, the whole system (all nodes) behave like a single system view.In case of Grid, every node is autonomous .
=>In case of Grid, Managed by its own resource manager and In case of Cluster, managed by centralized resource manager.