In this scenario each node is removed from the cluster, upgraded and then brought back online until all nodes are running the newest version.
Important
This method is currently broken between Pacemaker 0.6.x and 1.0.x
Measures have been put into place to ensure rolling upgrades always work for versions after 1.0.0 If there is sufficient demand, the work to repair 0.6 -> 1.0 compatibility will be carried out. Otherwise, please try one of the other upgrade strategies. Detach/Reattach is a particularly good option for most people.