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From Dain Sundstrom <>
Subject Re: Effectiveness of WADI's Design and Implementation Comforted
Date Fri, 19 Oct 2007 00:17:49 GMT
I'd also like to see a sticky test as most of the clusters I have  
worked with use a high-end hardware load balancer (although I do find  
this test very interesting).  I'd also like to see the test use a  
larger and mutating session.  One of the things that will effect  
latency is the time (and effort) it takes to move the session data.   
With people sticking large caches of detached JPA objects in sessions  
now days, I'd like to know how that effects my application performance.

Finally, how about a wadi vs tribes on Tomcat?

BTW you should talk to Jason about testing this on GBuild, so you can  
test in a true distributed state.


On Oct 18, 2007, at 12:02 AM, ikarzali wrote:

> jgenender wrote:
>>> Excerpt of the conclusion:
>>> "
>>> The effectiveness of the design and implementation of WADI's  
>>> distributed
>>> session lookup engine and replication engine is further comforted  
>>> by the
>>> observed average response times and scalability characteristics.
>>> For the considered scenarios, WADI performs better than Terracotta,
>>> which is not really surprising as...
>> If I may comment here...Without fine-grained clustering  
>> capabilities, I
>> have a hard time believing that WADI can outperform Terracotta.
>> Especially with large objects...WADI would push over the entire  
>> object
>> each time, where Terracotta would only ship the changed members.   
>> If you
>> are going to publish the numbers you did, you probably should explain
>> what is getting pushed across.
> Interesting test of Terracotta.  I wouldn't trust any test that  
> pegs the CPU
> at 100%.  May I suggest the following potential changes:
> 1. Running Jetty, Grinder, and Terracotta on a single laptop should  
> change.
> Run Terracotta on its own server.  It will run faster even though  
> it won't
> be over loopback.
> 2. Run sticky and see what happens.  See, the test is not testing  
> the same
> thing with WADI and Terracotta.  With WADI, the clustering  
> implementation is
> configured to keep data on  a finite number of nodes.  With  
> Terracotta, you
> have a consistent clustered view of sessions.  Since you are round- 
> robin,
> with Terracotta every node is holding a reference to every session  
> and as
> the sessions change, all Jetty nodes are updated with the change.   
> So, round
> robin WITH WADI replication off is actually pretty much cheating  
> because TC
> has the sessions in all nodes and WADI has them in one.  Run sticky  
> sessions
> in your load balancer.  Then Terracotta will have the session in  
> one node
> just like WADI.  _Then_ you will have apples-to-apples and maybe  
> find TC
> latency to be lower and throughput higher.
> I would be happy to help explain more but this use of WADI and  
> Terracotta
> seem like you are getting opposite behaviors out of the products  
> (full n-way
> replication with no SPoF under Terracotta versus zero replication  
> under
> WADI) and a different test will more accurately reflect the relative
> performance of the systems.
> --Ari
> -- 
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