Let's begin with the how. The partitioning is implemented in two ways -- firstly, in the same way as LPAR under V4R5 -- i.e. one partition per processor. But the second implementation is more interesting Ð one OS/400 partition and up to three Linux ones on a single processor 270 box and up to seven Linux partitions on a dual processor model. The 8xx series will support more partitions -- however, each processor will still only support a maximum of four partitions.

A partition can be limited to 10% of CPU for a particular processor, so the Linux partitions can be set up to have little overall impact on the base OS/400 core applications. This implementation appears to be based around the microcode originally written to support SSP on the Advanced/36 boxes, and as such will allow the Linux instances to use and share aggregated virtual I/O. If this is the case, it offers some interesting possibilities. What is certain is that the Linux partitions will be managed from Ops Navigator, which means that OS/400 is a hypervisor -- so the partitions should be able to be controlled on the fly, using some programmed intelligence.

Which flavours of Linux are supported? Well, right now, none -- the commercial distributors of Linux, Red Hat, TurboLinux, Caldera Systems and SuSE are unlikely to have distributions ready (they have taken an awful long time to get the zSeries ports out of the door) -- but, like the zSeries, it's likely there will be a "technical preview" release to allow those who want to do it themselves to get started. IBM are rumoured to have already ported the GNU Utilities to the iSeries to get the developer ball rolling.

Strategy

So, why put Linux on the iSeries? IBM's future strategy embraces Linux as a core operating platform, and as such any failure to make it available natively on the iSeries would be tantamount to announcing end of life for the poor old 400. I suspect that IBM also see Linux strategically as a corporate workgroup server O/S, taking market share from Microsoft. This would position the iSeries nicely as a line-of-business and multiple workgroup server for an SME -- with reduced cost of ownership compared with multiple NT servers. And finally, there are thousands of niche and mainstream applications available for Linux that haven't been ported to the iSeries -- so IBM get additional routes to market through a new business partner community.

So what could you use your shiny new Linux partitions for? Well, much as I love the iSeries as a line-of-business machine and as an e-commerce platform, even I admit that there are some things it doesn't do very well. For instance, the implementation of Domain Name Serving, whilst getting better with each release, isn't by any means state of the art. Anyone who has tried to use Net Server for file and print serving knows that it is not quite the best thing since sliced bread. And while you can use the iSeries for POP3 email, where is the web mail front-end for your users when they are on the road?

Now, Linux partitions can help with these situations. For example, you can run the latest build of BIND for your DNS, SAMBA to look after file serving, Send mail to handle your enterprise e-mail, with one of a number of free web-mail front ends -- and also use Leaf Node as a small NNTP server, so you can keep on top of comp.sys.ibm.as400.misc, and the Linux groups, while running your own internal discussion forums. And what about an Intranet search engine? And that's all in one partition.

Security

But where it gets really interesting is in the realms of e-commerce and security. Firewall/400 bit the dust a while back, but you can buy, and build, state of the art firewalls on Linux. So how about two firewalls, in separate partitions, one to guard your DMZ and the other to protect your network? Or multiple firewalls, that use artificial intelligence running under OS/400 to detect attacks and then collapse, block and reconfigure while the hacker thinks he has gained access to an inner level of security? And, as everyone knows, the initial point of attack on a webserver is to identify the flavour of webserver running, so the most secure method of presenting your e-commerce website is to use several servers running different HTTP server software. With multiple partitions, you can have Apache on one, Zeus on another, I-Planet on a third, AOLserver on a forth, and switch between them. The hacker says "too difficult" and goes off to find an IIS site.

So Linux partitions on the iSeries offer a wealth of solutions for different problems, and re-enforce the iSeries as a strong server platform -- at no real additional cost to the installation.