In dynamo's paper ,it says: Each key, k, is assigned to a coordinator node . The coordinator is in charge of the replication of the data items that fall within its range.
On Fri, Sep 3, 2010 at 2:56 PM, Benjamin Black <b...@b3k.us> wrote: > 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 > -- Best regards, Ivy Tang
