Bobby Woolf wrote:
>
> <vendor>
> This Extreme Clustering and Smart Load Balancing works across a network of
> server computers and is especially ideal for large server computers like a
> Sun E10000. Most app servers only start up a fixed number of VMs and have
> difficulty doing so with a limited number of VMs and IP addresses, so they
> only use a limited amount of the computer's capacity, which leaves unused
> capacity yet constrains scalability. In such a configuration, buying a
> larger box won't increase scalability, it just increases unused capacity.
> With GSJ, the number of VMs is unlimited by the app server, so the pool can
> grow to use all of the computer's resources. If you buy a larger box, you'll
> have more computer resources for more VMs which will give you more
> scalability.
> </vendor>
Bobby,
<vendor>
I am hard-pressed to believe your statement: "Most app servers only start up
a fixed number of VMs ... so they only use a limited amount of the computer's
capacity, which leaves unused capacity yet constrains scalability." In my
experience, it is very much possible to load a fully configured Sun E10000
with only 2-3 VMs. In fact, in my experience, running more than 2-3 VMs on
an E10000 actually reduces total throughput, due to the extra context-switching
and/or memory contention overhead. We have a performance tuning paper which
illustrates this point.
The scalability of a single VM is achived by multi-threading. You seem to
be suggesting that scalability is only possible with multi-processing. Although
I agree with you that 2-3 years ago, the threading capabilities of most VMs
was poor enough that you had to resort to multi-processing to scale your Java
code, today this is very much achievable by multi-threading, which is typically
also a much better way to scale, in terms of system resource utilization.
I am wondering if your performance results are up-to-date, or perhaps reflect
the limitations of VMs and/or threading libraries of a few years ago. Again,
today we (and probably most others) are able to scale very well with only
2-3 VMs per box.
</vendor>
-jkw
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