----- Original Message -----
From: "Evan Ireland" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Friday, February 09, 2001 6:04 AM
Subject: Re: Entity beans, clistering and scalability
> Jeff Schnitzer wrote:
> >
> > Pardon my (perhaps) naivete, but why on earth would starting multiple
> > VMs on the same box increase scalability? It would seem like you're
> > just going to consume a lot of extra resources, when all you really
> > should need to do is start more threads.
[snip]
> >
> > Please tell me what I'm missing.
Where should I start.... 8^)
One of the steps in tuning a VM is to determine the maxumum number of
threads that it will support before performance bogs down. It will bog
down for a number of reasons to do with thread management. Depending
upon you're applications footprint on the VM, you'll typically see VM
performance degradation at about 70 threads. I believe that the number of
VM threads is a tunable paramater in WL (which ties into their clustering).
Gemstone/J also tried to control this but using a different mechanisum.
The other factor that affects performance is the size of the VM. These
two factors by them selves indicate that heavier applications will do much
better if they utilize more than one VM. This corrolates well with my
experiences tuning EJB applications. FWIW, I've never seen a single VM
even come close to tapping out an E10K.
>From my vantage point, the vendors that are making scalability claims
support
multiple VM deployments. The question is, which mechanisums, work, are
easily configurable, easy to deploy, and really do offer a performance
advantage.
Oh and BTW, do they help with stability and avaliability. For instance, if
you're
single VM blows, then what?
<vendor>
I didn't use these tags in the previous paragraph because that was straight
java stuff.
GemStone/J has the capability to launch several VM's on the same hardware
in the same ip space. It does this out of the box with no special
requirements
for hardware or software to support this functionality. I contend that
administrators
love this because, the can contain the entire application server on a single
piece of
hardware if they so desire without setting up separate ip spaces. The VM
pool
sizes adapt to changes in the load on the system. A single VM/ip space
strategy
cannot dynamically add more ip spaces and consequently cannot dynamically
launch more
VMs.
GSJ's VM pooling also helps with stability and availability as old stale
VM's can
be rolled out of the system seamlessly. The application server can support
different
versions of the same application running at the same time. This offers a
very flexible
migration possibilities. You can upgrade the application without having to
take down
the system.
Point is many of these things are easy because of how the systems supports
multiple
VMs.
</vendor>
Kirk
[EMAIL PROTECTED]
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