On Thu, Sep 2, 2010 at 8:19 PM, Ying Tang <ivytang0...@gmail.com> wrote: > 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 ?
The coordinator node is the proxy node. > 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 ? Depends on the CL requested. QUORUM and ALL cause the RR to be performed by the coordinator. ANY and ONE cause RR to be delegated to one of the replicas for the key. > 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 ? > For writes, the coordinator sends the writes directly to the replicas regardless of CL (rather than delegating for weakly consistent CLs). > 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? > Sorry, I can't even parse this. b
