1. We ran jBoss/Tomcat on Linux using a creaking old 166MHz Pentium with
64MB RAM and 256MB swap space. This configuration thrashed noticeably
because of memory limitations, but we tested with our load simulator and
the system never fell over. Enormous amounts of memory are consumed by
the Hypersonic SQL engine which comes in the box with jBoss, and it is not
appropriate for production use. When we switched to PostgreSQL running on
the same machine and totally deconfigured Hypersonic in jboss.jcml, the
memory requirements dropped and performance was actually quite tolerable.
Note that I am not recommending you run such a system in production, but I
thought knowing this would help you gauge just how far you can push things
toward minimum.
2. In our experience, the bottleneck on Linux is not connection count but
thread count. As I have discussed in two immediately prior posts here,
jBoss under heavy load will exhaust the systemwide supply of task slots
and essentially wedge. This can be worked around by modifying the kernel
source and recompiling the kernel with a higher number of task slots. In
theory, changing to the "green threads" configuration would remove the
thread count limitation at the expense of performance.
3. In turn, the limiting factor on thread count is demand resulting from
the internal architecture of jBoss. I really do not know enough to
discuss this issue, but I understand it is a development concern.
In general, jBoss on Linux benefits from throwing as much RAM and CPU
resources at it as can be reasonably afforded. This is doubly a concern
when you run the database back-end on the same machine as the jBoss
application server. Our current test configuration is a dual 300MHz
Pentium III system with 256MB RAM, and I would probably not put quite that
low-powered a machine into production use. On the other hand, with our
present test configuration, the swap file is so far untouched with under
90MB actually utilized:
total used free shared buffers cached
Mem: 257640 235616 22024 65512 116680 36996
-/+ buffers/cache: 81940 175700
Swap: 1048560 0 1048560
My advice is to buy as much CPU power as you can at the outset because
this is expensive to upgrade later, and install whatever memory you think
you can get away with while keeping as many RAM slots unused as possible.
Since memory is very cheap now, adding more will just be a matter of
filling up those slots. Even 1GB or 2GB RAM is entirely affordable now.
Fast disks will also help the back-end database a lot.
If you are going to use more than two CPUs or exceed 2GB RAM, you are
strongly advised to run the 2.4 Linux kernel.
-- Mike
On 2001-06-24 at 09:45 -0700, Richard Bottoms wrote:
> Since the question has been raised about the maximum user load of JBoss I'm
> in need of some concrete numbers as far as is currently known.
>
> 1. What is the minimum configuration recommended
>
> 2. What's the maximum concurrent connections allowed under Linux.
>
> 3. Is this affected by processor speed, memory or chip type?
>
> I have a commercial app I want to develop, but I, and I would guess others
> need these answers if we are to proceed.
>
>
> Thanks,
> r.b.
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