Hi Ben,
    Thanks for the quick response. 
    It's clear about the example for single row/partition. However, normally 
data are not single row. Then for this case, I'm still confused. 
    The link above gives an example of 10 nodes cluster with RF = 3. But the 
figure and the words in the post shows that the coordinator only contact/read 
data from one replica, and operate read repair for the left replicas. 
    Also, how could read accross all nodes in the cluster? 

From: ben.sla...@instaclustr.com
Date: Tue, 20 Sep 2016 04:18:59 +0000
Subject: Re: Question about replica and replication factor
To: user@cassandra.apache.org

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).
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 SlaterChief Product OfficerInstaclustr: Cassandra + Spark - Managed 
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