Vnodes and ring in cassandra

[Inquistive allen]

Hello Team,

I am a newbie in cassandra. I have asked this question on various platforms but never got a satisfying answer.

Hence thought of bringing up the topic here. Sorry for this might be a simple question and also nowhere related to TLP tools.

1. I studied the paper on consistent hashing (which is being implemented in Cassandra)

2. Cassandra has the concept of Vnodes. The vnodes( As I understand a Vnode is a collection of Hashes) , are the basic blocks of replication in cassandra. It is the vnodes which are replicated across the cluster. Please do correct me I'm wrong

3. Suppose I have a Keyspace A with replication factor 3 and Keyspace B with replication factor 2. 

4. Is it that a Vnode is a collection of hashes of data from various Keyspaces.

5. In that case, Keyspace with varying replication factors , replicating them to other nodes would be a problem

6. Now from the consistent hashing paper, I get a feeling  that , ach Keyspace has a different ring. Also the name "KEYSPACE", points to a ring of keys in the ring.

    So is it that each keyspace has a different ring. If it is so, everything else like replicating vnodes among nodes in the cluster would fall in place.

    Each Keyspace has a different ring ---> each Vnode has data of various tables from a given keyspace----> hence copies equal to RF is only made in the cluster.

I know I am missing something. This way of understanding thing might be wrong.

Kindly help me understand the same. As this would help me visualise repair, bootstrap, adding cluster, streaming operations in a much better way.

Sorry again as it is not the right platform for this query. TLP being a team of experts , I thought of posting the query here.

Thanks

Allen

[Jon Haddad]

Please direct questions about Cassandra to the Cassandra user list or the Cassandra Slack channel.  This list is for the discussion of our open source dev tools.

Here's the community page with the information you need to subscribe: http://cassandra.apache.org/community/

Jon

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