Assuming you are using the SimpleStrategy or the NetworkTopologyStrategy and one rack per DC. If you backed up every 2nd node you would get one copy *IF* all nodes were consistent on disk. That can be a reasonably large if that you need to monitor.

It's easier to back up all the nodes it will also make it easier to restore the cluster.


Aaron Morton
Freelance Cassandra Consultant
New Zealand


On 8/05/2013, at 8:54 AM, Kanwar Sangha <> wrote:

Hi If we have a RF=2 in a 4 node cluster, how do we ensure that the backup taken is only for 1 copy of the data ? in other words, is it possible for us to take back-up only from 2 nodes and not all 4 and still have at least 1 copy of the data ?