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From John Pyeatt <>
Subject Re: replication_factor: ?
Date Fri, 07 Mar 2014 15:37:50 GMT
You really don't want to set your RF to the same value as the number of
nodes in your cluster for a variety of reasons. The biggest one being that
if you have a node go down, your entire database is essentially down
because you will be unable to fulfil any requests because the RF can never
be met.

The number of nodes in the cluster is essentially independent from your
replication factor.

The more important relationship is between your RF value, latency, and what
consistency level you want to use for your reads and writes.

If you are going to use QUORUM consistency level it makes a little more
sense to have your RF set to an odd number.

So for example if you have a 12 node cluster with an RF=3 and you are using
QUORUM consistency that means that 2 nodes ((RF+1)/2) have to be able to
fulfil the request.

On Fri, Mar 7, 2014 at 9:26 AM, Daniel Curry <>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?
>    We are using both 3.2.4 and 3.1.3 ( that will be upgraded to 3.2.4).
> Thank you.
> --
> Daniel Curry
> Sr. Linux System Administrator, Network Operations
> PGP : AD5A 96DC 7556 A020 B8E7 0E4D 5D5E 9BA5 C83E 8C92
> Arrayent, Inc.
> 2317 Broadway Street, Suite 20
> Redwood City, CA 94063
> 650-260-4520

John Pyeatt
Singlewire Software, LLC

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