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From Jonathan Ellis <jbel...@gmail.com>
Subject Re: Capacity problem with a lot of writes?
Date Thu, 25 Nov 2010 19:20:47 GMT
You want your memtables "as large as is reasonable, but not too
large."  Sounds like yours are too large.  As a first step, I would
strongly recommend upgrading to 0.6.8 and reducing the compaction
priority: http://www.riptano.com/blog/cassandra-annotated-changelog-063

On Thu, Nov 25, 2010 at 12:32 PM, Carlos Alvarez <cbalvarez@gmail.com> wrote:
> Hello All.
>
> I am facing a (capacity?) problem in my eight nodes cluster running 0.6.2
> patched with CASSANDRA-1014 and CASSANDRA-699.
>
> I have 200 writes/second on peaks (on each node, taking into account
> replication), with arow size of 35kb. I configured the memtable size to 1GB,
> the biggest size my heap seems to tolerate. With this configuration, the
> cluster is writing a sstable each 5 mins.
> When I decrease the memtable size I run into a minor compaction storm.
> However, the 1GB memtable forces me to have a hughe heap and makes me living
> on the edge of the memory.
> The question is:
> - Do I need more power in order to write less than 1GB each five minutes?
> - Has anyone experience with heaps of more than 8GBs?
> - Are the standard minor compaction thresholds usually enough for high
> loads? Or is something I am supposed to tune?.
>
> Thanks!
> Carlos.
>
>
> --
> Tal vez hubo un error en la grafía. O en la articulación del Sacro Nombre.
>



-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com

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