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From Ying Tang <ivytang0...@gmail.com>
Subject the process of reading and writing
Date Fri, 03 Sep 2010 03:19:35 GMT
Recently , i read the paper about Cassandra again .
And now i have some concepts about  the reading and writing .

We all know Cassandra uses NWR ,
When read :
the request ---> a random node in Cassandra .This node acts as a proxy ,and
it routes the request.
Here ,
1. the proxy node route this request to this key's coordinator , the
coordinator then routes request to other N-1 nodes   OR   the proxy routes
the read request to N nodes ?
2. If it is the former situation , the read repair occurs on the  key's
coordinator ?
   If  it is the latter , the  read repair occurs on the proxy node ?

When write :
the request ---> a random node in Cassandra .This node acts as a proxy ,and
it routes the request.
Here ,
3. the proxy node route this request to this key's coordinator , the
coordinator then routes request to other N-1 nodes   OR   the proxy routes
the request to N nodes ?


4. The N isn't the data's copy numbers , it's just a  range . In this  N
range , there must be W copies .So W is the copy numbers.
So in this N range , R+W>N can guarantee the data's validity. Right?




-- 
Best regards,

Ivy Tang

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