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From Ben Kaehne <ben.kae...@sirca.org.au>
Subject Re: Maximum load per node
Date Thu, 07 Jun 2012 12:59:36 GMT
Does this "max load" have correlation to replication factor?

IE a 3 node cluster with rf of 3. Should i be worried at {max load} X 3 or
what people generally mention the max load is?

On Thu, Jun 7, 2012 at 10:55 PM, Filippo Diotalevi <filippo@ntoklo.com>wrote:

>  Hi,
> one of latest Aaron's observation about the max load per Cassandra node
> caught my attention
>
> At ~840GB I'm probably running close
> to the max load I should have on a node,
>
> [AM] roughly 300GB to 400GB is the max load
> Since we currently have a Cassandra node with roughly 330GB of data, it
> looks like that's a good time for us to really understand what's that limit
> in our case. Also, a (maybe old) Stackoverflow question at
> http://stackoverflow.com/questions/4775388/how-much-data-per-node-in-cassandra-cluster
,
> seems to suggest a higher limit per node.
>
> Just considering the compaction issues, what are the factors we need to
> account to determine the max load?
>
> * disk space
> Datastax cassandra docs state (pg 97) that a major compaction "temporarily
> doubles disk space usage". Is it a safe estimate to say that the Cassandra
> machine needs to have roughly the same amount of free disk space as the
> current load of the Cassandra node, or are there any other factor to
> consider?
>
> * RAM
> Is the amount of RAM in the machine (or dedicated to the Cassandra node)
> affecting in any way the speed/efficiency of the compaction process?
>
> * Performance degradation for overloaded nodes?
> What kind of performance degradation can we expect for a Cassandra node
> which is "overloaded"? (f.i. with 500GB or more of data)
>
>
> Thanks for the clarifications,
> --
> Filippo Diotalevi
>
>
>


-- 
-Ben

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