[Building Sakai] More tomcats or bigger tomcats?

[Aaron Zeckoski]

It depends a lot on usage but for some things (confluence/jira) having
too much memory allocated will cause the JVM to sawtooth and
effectively thrash the memory and run poorly. Grails/groovy apps run
better with a large perm space and not very big heap because of the
dynamic nature of groovy. I don't think you will find there is a
general answer that works for all Sakai installs, but if people can
provide some numbers of students and usage patterns then it might be
easier to pin down best practices.

-AZ


On Thu, Sep 17, 2009 at 4:03 AM, John Bush <john.bush at rsmart.com> wrote:
> well, I don't have an answer for you, but I'm interested to know as
> well.  We are doing some performance testing right now and this is one
> of things I want to look at.  I think most people on 64 bit platforms
> are running heaps much bigger than 2 GB.  We are going to be looking
> at 1 8GB tomcat vs 2 4 GB tomcats, I don't think our current setup
> lets us look at anything bigger than that.  Hopefully I should have
> some results next week, I'll let you know what we figure out.
>
> John Bush
> Development Manager
> rSmart
>
>
>
>
> On Sep 16, 2009, at 11:59 AM, Joshua Swink wrote:
>
>> Is it better to run more tomcat instances, sticking with the default 2
>> GB heap size, or to run a single tomcat per CPU, using as much memory
>> as can be allocated to each one?
>>
>> We currently run four tomcat instances on two machines, load balanced
>> through Apache. Each one has the recommended 2 GB heap size.
>>
>> Our user load is always on the increase, and I was wondering what is
>> the better configuration:
>>
>> - Increase the heap size on each tomcat's JVM? Perhaps to 3 GB.
>> - Leave the heap size at 2 GB and run additional tomcat instances.
>>
>> Our current servers have 16 GB memory, so that works out to about 4-5
>> tomcats per machine if we stay at 2 GB heap per instance. My main
>> question is whether people have experienced better performance using
>> more 2 GB tomcats, or fewer tomcats with larger heap sizes.
>>
>> Also, our servers have 2 CPUs each.
>>
>> Thanks for any advice!
>>
>> --
>> Joshua Swink
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-- 
Aaron Zeckoski (azeckoski (at) vt.edu)
Senior Research Engineer - CARET - University of Cambridge
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