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
