2 vs 1 instance of WLS ?

Question

Greetings !!!
Leaving other parametes same, would 2 instances of WLS with smaller
values of Heap size, executeThreadCount, DBConnections etc. each would
provide better perfrormance than one instances of WLS with higher number
for these paramaters ? Has anyone done benchmarks for such a scenario???
Environement: 2-CPU box, 1GB RAM, Solaris 6, JDK_1.2.2_05a & WLS
5.1-SP5
Thanks for your help/suggestions/pointers???
Sam

Answer 1

Mike,
Originally, the 'more, smaller instances' was a work-around for poorgarbage
collection. I believe that the later JDK's are much better at it. Wouldn'tit
make more sense to simply fix the garbage collection?There is the GC issue, but it is mostly a non-issue now with Hotspot. IBM's
JDKs also have much-improved GC implementations.
It's a queuing theory thing - 1 pool of 50 db connections will be able tostand
more load than 2 pools of 50 db connections, or 10 pools of 5 dbconnections.
Same goes for execution threads.Au contraire ... the front queue (e.g. a hardware load balancer) may
subscribe to that theory, but consider the bank vs. the check-out line
example from CS 101.
However, I don't believe that is the real issue. It's all about how many
requests you complete per second per unit of hardware. Obviously if one
instance works the best, then you stick with that.
Oh, I forgot one - when you start up a cluster with many instances, yournetwork
traffic goes wild. I think this was fixed around 4.5.1 SP 10.Are you telling me that there was a release of WL before 5.1? ;-)
And they have 'director' in front of their names.See below.
Peace,
Director Cameron Purdy
Tangosol, Inc.
http://www.tangosol.com
+1.617.623.5782
WebLogic Consulting Available
"Mike Reiche" <[email protected]> wrote in message
news:[email protected]...
>
"Cameron Purdy" <[email protected]> wrote:
Hi Mike,
Someone needs to send this to www.urbanlegends.com.I'd like to do some testing with WL6.0/JDK1.3/Hotspot 2.0/Solaris 8 etc.,
and in that case you might be right. On some systems, you can crank the
execute threads way up and it won't make a difference -- the system will
not
get saturated.Originally, the 'more, smaller instances' was a work-around for poorgarbage
collection. I believe that the later JDK's are much better at it. Wouldn'tit
make more sense to simply fix the garbage collection?
Let's see what else - you also have to cut your connection pool sizes
in
half.
Most apps keep the pool size about the same as the exec thread count.It's a queuing theory thing - 1 pool of 50 db connections will be able tostand
more load than 2 pools of 50 db connections, or 10 pools of 5 dbconnections.
Same goes for execution threads.
Oh, I forgot one - when you start up a cluster with many instances, yournetwork
traffic goes wild. I think this was fixed around 4.5.1 SP 10.
We run two instances per box here and I wish we didn't.Based on your stated feelings, is there any reason why you run two
instances
per box?Because there are people here that read about what what a great
idea it was. And they have 'director' in front of their names.
Cameron Purdy
Tangosol, Inc.
http://www.tangosol.com
+1.617.623.5782
WebLogic Consulting Available
"Mike Reiche" <[email protected]> wrote in message
news:[email protected]...
Someone needs to send this to www.urbanlegends.com.
Using two instances vs. one instance doubles all kinds of things -
memory
required, overhead,
context switching, all class loading and JSP compiling, configuration
and
maintenance. And if you
use the same jsp workingDir for both WLS the two WLS will overwrite
each
other's generated
class files. (and they don't warn you about that in the doc). Let's seewhat else - you also have
to cut your connection pool sizes in half.
If you're not getting enough concurrency, then increase the number ofexecuteThreads.
If you want reliability, then fix whatever is breaking. It always
better
to not fail than to
recover nicely from a failure.
We run two instances per box here and I wish we didn't.
Mike
"Cameron Purdy" <[email protected]> wrote:
Sam,
It is best to test with your particular application but ... in most
cases,
adding a second instance of WebLogic to a particular host will make
more
effective use of the processor(s) in the server. Since you are payingper
processor, why not take full advantage of them? ;-)
Also, using two network interfaces, you can bind one WL instance to
one
NIC
and the other WL instance to the other NIC and thus not lose the site
if
one
of the networks goes down. (I don't know yet how to force WL to
assign
the
secondary from the other network, though.)
The main variable that you are looking for is throughput: Can you
handle
more concurrent requests? This measurement is basically the number of
typical requests per period of time that are possible before you seethe
server queues growing. In other words, once the server queues start
growing, that means that your cluster isn't managing to keep up, andyou
have lost the war.
Peace,
Cameron Purdy
Tangosol, Inc.
http://www.tangosol.com
+1.617.623.5782
WebLogic Consulting Available
"sam ernie" <[email protected]> wrote in message
news:[email protected]...
Greetings !!!
Leaving other parametes same, would 2 instances of WLS with smaller
values of Heap size, executeThreadCount, DBConnections etc. each
would
provide better perfrormance than one instances of WLS with highernumber
for these paramaters ? Has anyone done benchmarks for such ascenario???
Environement: 2-CPU box, 1GB RAM, Solaris 6, JDK_1.2.2_05a & WLS
5.1-SP5
Thanks for your help/suggestions/pointers???
Sam