Has anyone successfully been able to upgrade Red Hat 9.0 to Enterprise Linux 3 AS (i386) ???

Even though everyone recommends doing a clean install, in theory is seems possible to upgrade but I haven't heard any success stories yet ...

Has the file system and structure really changed that much?

I would really try and avoid this... In general, Red Hat don't even support upgrading from one version of AS to another (e.g. 2.1 to 3), so it is highly unlikely that an upgrade from a non-AS version would work.

Filesystem issues aside, you would most likely be left with binaries from RH9 RPM's lying about, and I think some of the RPM dependancy chains may have changed as well.

Red Hat recommend a complete reload when moving from one major version to another, and I don't think that they will support AS unless it has been installed from scratch.

This is, to my mind, still one of the biggest stumbling blocks that the so-called enterprise linux vendors need to overcome. It is not reasonable to expect enterprise organisations to take machines out of service, remove all applications, re-install the operating system, all applications and all data, and then re-insert the machine into service.

FreeBSD gets around this beautifully, so I'm not sure why the big boys in Linux land haven't got their act together on this one yet

Good answer here just as I expected ...
It's just odd that they expect corporations to spend $$ to migrate,
(expect) might be the wrong word here, more like force corporations.
I don't see the logic in that, because that would make corporations look into other options which might lead them in other directions.
It's a gamble, don't you think???

It's a huge gamble. This is hurting groups on two levels.

1. People who've been concerned about moving to Linux, but finally took the plunge for RH9 will be going _straight_ back to wherever the came from. This is a huge loss to the Linux movement.

2. A lot of people who now have to move off of RH9 may consider other distributions... SuSE, with it's current Novell investment and enthusiasm stood to clean up a chunk of the market if they played this event better, but they seem to have let it slip them by.

Red Hat still have the largest installed server base, but I think we will see this start to slip in the coming months. Their extreme costs for tools that other vendors, and even Microsoft provide for free (Update server solutions for example), the high cost of per sever support when compared to SuSE's incident support options and the fact that they don't seem to be doing anything to combat these events is very likely to hurt their market share.

The best thing about the marketplace at the moment is that Red Hat finally have a competitor in the Enterprise market. This has been lacking, and this lack has caused them to get complacent.