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From Jonathan Ellis <>
Subject Re: Batch writes getting slow
Date Thu, 06 Oct 2011 15:26:08 GMT
On Thu, Oct 6, 2011 at 10:09 AM, Stefan Reek <> wrote:
> I can see that during the times the writing gets slow there are ~3000
> pending tasks, but they disappear quickly.

Your best bet is to make the write load more constant and less bursty.
 If you really do need to handle bursts like that with low latency,
then you probably do need more hardware.  (But make sure you've
covered the basics first, like putting commitlog on a separate

> I can also see that Cassandra gradually takes more and more memory,
> eventually filling up the 16GB that is assigned to it, although it
> doesn't go out of memory.
> Is this normal behaviour? I expected to see more of a sawtooth...

Yes, that is normal from the OS's view of the JVM.  If you want to see
the sawtooth you'd need to look at the JVM's internal metrics, e.g.,
with jconsole.

Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of DataStax, the source for professional Cassandra support

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