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From Alaa Zubaidi <>
Subject Re: 0.7 memory usage problem
Date Mon, 27 Sep 2010 19:59:22 GMT
  Thanks for the help.
we have 2 drives using basic configurations, commitlog on one drive and 
data on another.
and Yes the CL for writes is 3, however, the CL for reads is 1.

You are saying I am doing 36000 inserts per second, when I am inserting 
600 rows, I thought that every _row_ goes into one Node, so the work is 
done for a _row _not a _column_, so my assumption is NOT true, the work 
is done on a column level? so if I reduce the number of columns I will 
get a "substantial" improvement in performance?

Also, what do you mean by "distributing the client load across the 
cluster",  I am doing the writing on Node1, the reading on Node2, and 
the maintenance on Node3 (disabled the maintenance for now).
Do you think its better if I do writes on all 3 Nodes and reads on all 3 
Nodes as well?


On 9/26/2010 3:41 PM, Peter Schuller wrote:
>> It is odd that you are able to do 36000/sec _at all_ unless you are
>> using CL.ZERO, which would quickly lead to OOM.
> The problem with the hypothesis as far as I can tell is that the
> hotspot error log's heap information does not indicate that he's close
> to maxing out his heap. And I don't believe the JVM ever goes for OOM
> for GC efficiency reasons without the heap actually having reached
> it's max size first.
> I don't disagree with what you said in general, it just seems to me
> that something else is going on here than just plain memory churn
> based on both the seeming lack of a filled heap and the hotspot log's
> claim that the culprit was a stack overflow rather than heap overflow.
> One thing to try may be to run without concurrent GC (on the
> hypothesis that there is some corruption issue going on). The problem
> is that even if that fixes the problem it proves very little about the
> root cause and is not necessarily useful in production anyway
> (depending on heap size and latency requirements).
> Another thing is to try simply increasing the stack size, but again if
> this happens to work it's hiding the real problem rather than being a
> real fix (on the premise that there is no legitimate significant stack
> depth).
> I'm not sure what the best course of action is here short of going
> down the path of trying to investigate the problem at the JVM level.
> I'm hoping someone will come along and point to a simple explanation
> that we're missing :)

Alaa Zubaidi
PDF Solutions, Inc.
333 West San Carlos Street, Suite 700
San Jose, CA 95110  USA
Tel: 408-283-5639 (or 408-280-7900 x5639)
fax: 408-938-6479

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