[Deploying Sakai] Performance optimisation with Oracle

Remi Saias remi.saias at hec.ca
Wed May 5 14:38:44 PDT 2010

Thanks Julian for sharing your opinion. Actually I did not see any 
change of performance when we
switched from full RAC mode to single node.

We will try in the following weeks to improve our performance on a 
single, local and dedicated
instance and then get back on the RAC and see how it goes... we sure do 
need redundancy, but if
performance is not good enough, our users won't love it!


-------- Message original --------
Sujet : Re: [Deploying Sakai] Performance optimisation with Oracle
De : Julian M. Morley <jmorley at stanford.edu>
Pour : production at collab.sakaiproject.org
Date : 2010-04-28 18:15
> On Wed, Apr 28, 2010 at 3:00 PM, Martin B. Smith <smithmb at ufl.edu> wrote:
>> On 4/28/2010 5:10 PM, Remi Saias wrote:
>>> Hello,
>>> We are running some load testing on one of our future Sakai 2.6.1
>>> production server and our DBA noticed a problem he described as
>>> "contention with frequent inserts and updates on 2 tables: sakai_session
>>> and sakai_presence which causes a lot of "CPU + Wait for CPU" wait events".
>>>  From my point of view I see that our current performance is at least 2
>>> times slower than what we achieved on our previous pilot instance which
>>> was running with mySQL and even more annoying is that the performance
>>> (in transaction per second) is quickly decreasing when I raise the
>>> number of simulated students in my tests (using The Grinder).
>>> We are using Oracle 10g in a RAC architecture. Anybody have encountered
>>> such problems or have any clue to how we could improve this situation?
>>> I can provide a lot more details if required! :-)
>>> Thanks in advance!
>>> Remi Saias for the Sakai/OpenSyllabus team at HEC Montreal
>> Hi Remi,
>> Can you tell if this is contention between RAC nodes for the blocks that
>> comprise those 2 tables, or if you're seeing contention even when a
>> single RAC node is running by itself?
> It certainly sounds like the expected behavior of RAC 10g trying to
> write to the same table from two different nodes, doesn't it?
> Remi, FWIW, I'd recommend either using 10g in primary/failover mode
> (all queries go to one node, second node used only if the primary
> fails) or upgrading to 11g if possible - 11g includes some
> improvements for these kinds of write-contention issues in RAC. And
> remember that RAC is for redundancy, not for performance. :-)

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