On 8 April 2014 09:29, vck <veesee...@gmail.com> wrote: > After reading through the vnodes and partitioning described in the > datastax documentation, I am still confused about how rows are > partitioned/replicated. > > With vnodes, I know that each Node on the ring now supports many token > ranges per Node. However I am still not very clear on how the replication > is carried out. > > If I have 4 Nodes A, B, C, D and their ranges are below. > > A - [1,2,3,4] > B - [5,6,7,8] > C - [9,10,11,12] > D - [13,14,15,16] > > After a shuffle, lets assume the Nodes are shuffled like this. > > A - [1,5,13,9] > B - [2,6,14,10] > C - [3,7,15,11] > D - [4,8,16,12] > > now if I use a simple replication strategy and RF=3, the first replica > rowkey gets placed on node determined by the partitioner. > > Prior to vnode, if my rowkey hash is 2, it gets placed on Nodes A, B, C. > With the above vnode setup, if my rowkey hash is 2, does it get placed in > B, C, D ? > Yes. The only difference vnodes makes to the calculation of where replicas live is that replicas are not placed on the same node.
Richard.
