Each individual read (where a read is a single row or single partition) will read from one node (ignoring read repairs) as each partition will be contained entirely on a single node. To read the full set of data, reads would hit at least two nodes (in practice, reads would likely end up being distributed across all the nodes in your cluster).
Cheers Ben On Tue, 20 Sep 2016 at 14:09 Jun Wu <wuxiaomi...@hotmail.com> wrote: > Hi there, > > I have a question about the replica and replication factor. > > For example, I have a cluster of 6 nodes in the same data center. > Replication factor RF is set to 3 and the consistency level is default 1. > According to this calculator http://www.ecyrd.com/cassandracalculator/, > every node will store 50% of the data. > > When I want to read all data from the cluster, how many nodes should I > read from, 2 or 1? Is it 2, because each node has half data? But in the > calculator it show 1: You are really reading from 1 node every time. > > Any suggestions? Thanks! > > Jun > -- ———————— Ben Slater Chief Product Officer Instaclustr: Cassandra + Spark - Managed | Consulting | Support +61 437 929 798
