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From Donald Smith <Donald.Sm...@audiencescience.com>
Subject RE: replication_factor: ?
Date Fri, 07 Mar 2014 22:01:09 GMT
Robert, please elaborate why you say "To make best use of Cassandra, my minimum recommendation
is usually RF=3, N=6."

I surmise that with any less than 6 nodes, you'd likely perform better with a sequential/single-node
solution.  You need at least six nodes to overcome the overheads from concurrency.  But that's
a vague explanation.

Thanks, Don

From: Robert Coli [mailto:rcoli@eventbrite.com]
Sent: Friday, March 07, 2014 11:36 AM
To: user@cassandra.apache.org
Subject: Re: replication_factor: ?

On Fri, Mar 7, 2014 at 7:26 AM, Daniel Curry <daniel.curry@arrayent.com<mailto:daniel.curry@arrayent.com>>
wrote:
  I would like to know on what is the rule of thumb for "replication_factor:" number?
I think the answer is depends on how many nodes one has? IE: three nodes will be the
number 3.  What would happen it I put the number 2 for a three node cluster?

To make best use of Cassandra, my minimum recommendation is usually RF=3, N=6. There are certainly
valid use cases with lower RF or N but from what I can tell they are an order of magnitude
less common.

=Rob


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