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From Amit Chavan <cami...@gmail.com>
Subject Cassandra Counters and Replication Factor
Date Wed, 12 Oct 2011 07:37:50 GMT
Hi,

Looking at this talk (
http://www.datastax.com/wp-content/uploads/2011/07/cassandra_sf_counters.pdf)
by Sylvain Lesbresne at DataStax, I had a few questions related to my
understanding Cassandra architecture.

Assuming that we have a keyspace in Cassandra with:
1. Replication Factor (RF) = 1.
2. "Counters" as a counter column family having "row-key" as a row key which
has "cnt" as a counter column.
3. We always update Counters["row-key"]["cnt"] with a Consistency level of
ONE.

My understanding is that in such a case, the updates/second of that counter
will be limited by the performance of just one node in the cluster. Adding
new nodes will not increase the rate of update. However if RF was 3 (keeping
everything else same), updates/second would roughly have been 3 times the
current value. Am I correct here?

Moreover, any write operation to a column in a key in the above mentioned
configuration can scale only if RF increases. Is this inference correct?

-- 
Regards
Amit S. Chavan

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