> > > A few questions: > - Do we have a clear definition for a cluster? >
Cluster before federation is defined by list of datanodes in include file, bound together by namespaceID of the namenode that these nodes bind to on first registration with the namenode. In essence, namespaceID defines the cluster nodes. In federation cluster namenodes are setup with the same clusterID. ClusterID is established at the datanodes when they first register with a namenode. So nodes with the same clusterID are part of the cluster. - With the above definition, is it an error if not all DNs belong to the > same set of NNs? > A DN has to belong to same set of NNs sharing the same clusterID. DNs cannot register with a namenode that has a different clusterID. > - With the working definition of a cluster, what namespace guarantees are > given to clients? > I am not sure what you mean by this. > >
