> On Aug 17, 2019, at 10:53 AM, Inquistive allen <[email protected]> wrote:
>
> 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
Vnodes JUST mean each host has more than one token
> 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.
>
The easiest way to visualize most cassandra operations is to draw the tokens in
a circle. Vnodes means extra tokens
Replica sets are adjacent tokens. You steam from any node in the replica set in
the common replacement case, or the losing replica in the expansion case
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