On Mon, Mar 29, 2010 at 12:27 PM, Ned Wolpert <ned.wolp...@imemories.com> wrote: > Folks- > > Can someone point out what happens during a node failure. Here is the > Specific usecase: > > - Cassandra cluster with 4 nodes, replication factor of 3 > - One node fails. > - At this point, data that existed on the one failed node has copies on 2 > live nodes. > - The failed node never comes back > > First question: At what point does Cassandra re-migrate that data that only > exists on 2 nodes to another node to retain the replication factor of 3?
When you tell it to decommission the dead one. > Second question: Given the above case, if a brand new node is added to the > cluster, does anything happen to the data that now only exists on 2 nodes? No, Cassandra doesn't automatically assume that "this node is never coming back" w/o intervention, by design. (Temporary failures are much more common than permanent ones.) -Jonathan
