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From Peter Schuller <peter.schul...@infidyne.com>
Subject Re: munin is great for monitoring Cassandra
Date Thu, 17 Jun 2010 20:53:59 GMT
> drive on an EBS volume).  Does that pattern look bad or is it
> relatively normal? If it's not normal, any advice for what I should
> change to get better performance?

Assuming you're running with the default cassandra VM options or
similar (mainly, the CMS GC), the graph looks fairly normal to me. You
would tend to expect frequent small variations that are the result of
young-generation GC:s (ParNew:s), with some less frequent larger dips
in memory usage associated with CMS completing a concurrent mark/sweep
phase, typically triggered by used heap size approaching the current
heap size.

Normally the dips are somewhat indicative of the size of the actual
live set that your application is using; I'm not sure what's going on
in the middle of the graph with the dip being significantly higher.
Did you have very significant write activity during that period (but
it seems excessive even so).

-- 
/ Peter Schuller

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