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From srmore <>
Subject Re: Cassandra performance decreases drastically with increase in data size.
Date Mon, 03 Jun 2013 14:07:54 GMT
Thanks all for the help.
I ran the traffic over the weekend surprisingly, my heap was doing OK
(around 5.7G of 8G) but GC activity went nuts and dropped the throughput. I
will probably increase the number of nodes.

The other interesting thing I noticed was that there were some objects with
finalize() methods, this could potentially cause GC issues.

On Fri, May 31, 2013 at 1:47 AM, Aiman Parvaiz <>wrote:

> I believe you should roll out more nodes as a temporary fix to your
> problem, 400GB on all nodes means (as correctly mentioned in other mails of
> this thread) you are spending more time on GC. Check out the second comment
> in this link by Aaron Morton, he says the more than 300GB can be
> problematic, though this post is about older version of cassandra but I
> believe concept still stands true:
> Thanks
> On May 29, 2013, at 9:32 PM, srmore <> wrote:
> Hello,
> I am observing that my performance is drastically decreasing when my data
> size grows. I have a 3 node cluster with 64 GB of ram and my data size is
> around 400GB on all the nodes. I also see that when I re-start Cassandra
> the performance goes back to normal and then again starts decreasing after
> some time.
> Some hunting landed me to this page
> which talks
> about the large data sets and explains that it might be because I am going
> through multiple layers of OS cache, but does not tell me how to tune it.
> So, my question is, are there any optimizations that I can do to handle
> these large datatasets ?
> and why does my performance go back to normal when I restart Cassandra ?
> Thanks !

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