Split Brain

Split brain means that the Cluster is split in two (or more) parts, but both parts think they are the only remaining part of the cluster. This can lead to very bad situations when both parts of the cluster try to host the resources that are offered by the cluster. If the resource is a file system, and multiple nodes try to write to the file system simultaneously and without coordination, it may lead to corruption of the file system and the loss of data. As it is the purpose of a high availability cluster to avoid situations where data could be lost, this must be prevented no matter what. (Van Vugt 2014, 6)