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From "GB Developer" <gb107...@globallyboundless.com>
Subject RE: Tomcat's scalability
Date Mon, 19 Jun 2006 22:35:26 GMT
My feeling is that by calling an installatin of 'java' or 'the jdk/jre' a
'jvm' is going to produce confusion.

/usr/local/applications/tomcat1
/usr/local/applications/tomcat2
/usr/local/applications/tomcat3
/usr/local/java

That's one *JDK/JRE*, and 3 tomcat *instances*.

Each tomcat startup file uses the same JDK to launch a separate *JVM* (so 3
JVMs equates directly to 3 tomcat instances) because as Leon says, you can't
run 2 tomcats in a single JVM. 

So no need to install java more than once, just launch multiple JVMs (and
thus, multiple tomcats).

We do this on a single CPU box, because we find we 'need' to manage the
memory of the webapps running in each instance. So if we 'need' to bounce a
tomcat server because it's got 1% free and isn't getting any better, then we
still have the other two tomcats serving the websites they serve.  And I
always say 'need' in quotes because yes, one day we'll track down our leaks
and then we won't 'need' to do that.

Of course, we're still CPU-bound, so there's no real 'performance' or
'scalability' enhancement by having more than one instance on a single box.
We'd get that (I think) if we clustered more than one physical box each with
its own tomcat/jvm instance, or by clustering multiple tomcats on a a
single, multiple-cpu box.

That last paragraph is my own weak understanding of
CPUs/scalability/clustering, so could be off.


> -----Original Message-----
> From: Biernatowski Bartosz J [mailto:Bartosz.Biernatowski@rxsol.com] 
> Sent: Monday, June 19, 2006 4:55 PM
> To: 'Tomcat Users List'
> Subject: RE: Tomcat's scalability
> 
> 
> My understanding of Tomcat's instance is having both 
> Tomcat+JVM installed in separate directories. Both Tomcats 
> running on separate ports.
> 
> BJ Biernatowski
> Application Developer, e-Business
> 
> -----Original Message-----
> From: GB Developer [mailto:gb1071nx@globallyboundless.com] 
> Sent: Monday, June 19, 2006 2:40 PM
> To: 'Tomcat Users List'
> Subject: RE: Tomcat's scalability
> 
> How do you propose to add a 'separate instance of Tomcat' 
> without 'adding a separate JVM'? 
> 
> Or do you/others mean by 'instance of tomcat' = 'a separate 
> physical server with single instance of JVM/Tomcat' ?
> 
> > 
> > So far it sounds that the approach of adding separate
> > instance of Tomcat and using round robin is better than 
> > adding a separate JVM.
> > 
> 
> 
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