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."

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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 Pluta
david