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From Peter Schuller <>
Subject Re: Unable to repair a node
Date Sun, 14 Aug 2011 15:07:28 GMT
> i am always wondering why people run clusters with number of nodes == rf
> i thought you needed to have number of nodes > rf ti gave any sensible
> behaviour... but i am no expert at all

No. The only requirement is that the number of nodes be >= RF, since
clearly in a cluster with fewer nodes than RF you cannot satisfy RF.

You select your RF for purposes of redundancy and the consistency
level you wish to achieve, in combination with availability. Scaling
the cluster to sizes beyond RF is something you do for performance.
They're not tied, other than the "cluster size >= RF" restriction.

(I'm not being *entirely* correct; there are cases where a higher RF
makes sense for performance but I'd say they're sufficiently
obscure/specifc that that if you're in that position you hopefully
know it anyway.)

/ Peter Schuller (@scode on twitter)

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