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From Paul Loy <ketera...@gmail.com>
Subject Re: How to scale Cassandra?
Date Mon, 04 Jul 2011 09:59:26 GMT
That's basically how I understand it.

However, I think it gets better with larger clusters as the proportion of
the ring you move around at any time is much lower.

On Mon, Jul 4, 2011 at 10:54 AM, Subscriber <subscriber@zfabrik.de> wrote:

> Hi there,
>
> I read a lot of Cassandra's high scalability feature: allowing seamless
> addition of nodes, no downtime etc.
> But I wonder how one will do this in practice in an operational system.
>
> In the system we're going to implement we're expecting a huge number of
> writes with uniformly distributed keys
> (the keys are given and cannot be generated). That means using
> RandomPartitioner will (more or less) result in
> the same work-load per node as any other OrderPreservePartitioner - right?
>
> But how do you scale a (more or less) balanced Cassandra cluster? I think
> that in the end
> you always have to double the number of nodes (adding just a handful of
> nodes disburdens only the split regions, the
> work-load of untouched regions will grow with unchanged speed).
>
> This seems to be ok for small clusters. But what do you do with when you
> have several 100s of nodes in your cluster?
> It seems to me that a balanced cluster is a bless for performance but a
> curse for scalability...
>
> What are the alternatives? One could re-distribute the token ranges, but
> this would cause
> downtimes (AFAIK); not an option!
>
> Is there anything that I didn't understand or do I miss something else? Is
> the only left strategy to make sure that
> the cluster grows unbalanced so one can add nodes to the hotspots? However
> in this case you have to make sure
> that this strategy is lasting. Could be too optimistic...
>
> Best Regards
> Udo




-- 
---------------------------------------------
Paul Loy
paul@keteracel.com
http://uk.linkedin.com/in/paulloy

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