two-node cluster for riak?

Justin Sheehy justin at
Thu Apr 18 11:33:17 EDT 2013

Hi, Michael.

Your spidey-sense is absolutely correct.

Recall for a moment that Riak by default will store 3 copies of everything. This means that in a two-node configuration any given value will be stored once on one node and twice on the other. Not only does this mean a whole lot of wasted work, it removes much of the safety and availability that people look to get from Riak. If one node goes down, then for half of your keys you have lost a majority of their replicas.

On only two nodes, you can't really get the kind of fault-tolerance Riak provides... with Riak or any other software.


On Apr 18, 2013, at 11:26 AM, Michael Forrester wrote:

> Greetings Everyone,
> I am not sure if this is the right forum to ask this question, but here goes.
> We are currently running a six-node cluster in Amazon AWS.   There has been some talk by our architects of going to a two-node configuration using SSD-backed instances with super fast hardware, but for some reason this is triggering " this is not correct, but I don't remember why" spidey sense.  From my understanding, it is best to run riak with 5 nodes or at least N +2 and that a two-node cluster (even though the hardware will be way faster) will not satisfy that.   
> Any loose suggestions about how to approach this?   I am open to the two ultrafast nodes... I am not sure how to put riak on them to work in a fault-tolerant way.   
> Articles, dirty limericks, and soliloquies are all appreciated.  
> -- 
>  Michael Forrester
>  Director of Infrastructure
>  WorthPoint Corporation
> 404.996.1470 O)
> 404.939.6499 C)
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