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From Inquistive allen <inquial...@gmail.com>
Subject Consistent hashing vnodes and ring in cassandra
Date Sat, 17 Aug 2019 17:53:32 GMT
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.

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.

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