AS/400 and Java

Timor wrote:
"The major problem is runtime performance. A modest P-III 733 MHz
outperforms our model 270 at least 5 times (and up to 20 times) on our
load stress simulations, which mostly make use of JBoss MQ and data
queues through JT400."

And Stefan replied:
"thanks for your hints. I understood the IBM papers that  AS 400 is a really
fast  machine for java. But looks like it isn't."
=========

Hopefully one of the real heavyweights on Java performance will step in here
at some point (where are ya when we need ya, Blair???), but let me give you
my own less-than expert opinion.  In rality, the iSeries JVM is very
powerful, very scalable and very fast.  You have to be careful what you're
measuring when you compare PCs and midranges, though.

Timur is comparing the iSeries model 270, a single processor midrange
server, with a dedicated PC running a JVM.  That's usually an unfair
comparison, because the dedicated PC isn't doing any of the things the
AS/400 is doing in the background, and isn't capable of doing them, which is
why it can do one thing very fast.

The tradeoff for a midrange system is the ability to easily scale as opposed
to a low price for a small number of users.  With an AS/400, you can add
literally dozens of processors, to increase your capabilities hundreds or
even thousands of times.  Try that with your 733MHz PC, or even a PC
network.

The iSeries is not a single-task dedicated machine.  It is a business
server, and for that reason, raw single-use performance comparisons are
meaningless.  For example, does your PC have a built-in database?  No.  You
have to add that.  And tune it.  With the iSeries, it's all right there.
Can you run multiple partitions with your PC?  Piece of cake with the
iSeries.  Do you have object level security?  An RPG compiler?  5250
interface?  Nope.  Do you have hot-swap RAID drives?  Automatic disk arm
balancing?  Automatic system tuning?

All of this comes with the iSeries.  Because of that, it really doesn't show
its colors until you have a few dozen users.  It's kind of like an old car I
had - a 1972 Buick Electra 225 with a Wildcat 445 engine.  From 0-50, it
wasn't very quick, because it was a big, heavy car.  But from 50-90, there
wasn't a car on the highway that came close, even the fancy muscle cars.
See, the 225 was designed to be driven fast for a long time, and that's sort
of what the iSeries is built for - lots of user with lots of uptime.

So if you're looking for a server to replace something that's running fine
on a single-PC J2EE server, then the iSeries is probably the wrong way to
go.  I'd have to know more of the architecture to be sure, because I'm
assuming Timur doesn't need the database or security of an iSeries.  That
being the case, we could have a long discussion on why anyone would write a
J2EE application that can run on a single PC, but that's a different story
for a different day.

Now, if your application makes heavy use of a real enterprise database, or
you may need to scale up to dozens or hundreds of users, or you need 24/7
uptime, or you want to use business languages such as RPG or COBOL for your
business rules, then you might want to look into the iSeries.  The iSeries'
strength is not in the fact that you can throw together a quick, cheap
solution with little or no programming.  Instead, the iSeries strength lies
in its ability to integrate all the latest technologies, from Java to Linux,
along with proven legacy techniques such as RPG and COBOL, to allow you to
create powerful, scalable applications.

Or, you might want to have a server farm running an EJB application on a
bunch of PCs (thus providing failover), but all communicating with an
iSeries in the background for pure database and business logic serving.
That's a possible architecture, but it requires more than a simple stress
tester to determine whether it's the right architecture for you.

You really have to take the time to determine your business requirements
before you can even begin to compare servers.  Once you determine your
actual hardware needs, you may find that you have to compate the total cost
of ownership of an iSeries as opposed to a PC server farm with, say, a dozen
PCs.

On the other hand, if it turns out your application fits on a single PC,
then I doubt that you need an iSeries.  Instead, you might want to consider
something more appropriate, like Microsoft IIS and Visual Basic.

Joe