Hello, I am looking at having to work on a project that the customer is currently on CF 6 MX. They obviously need to upgrade and so I am looking to experiences, thoughts, advice, anything at all about doing an upgrade over this many versions. The major question I have is should we go major version to major version and not skip, like 6-7, etc. or is it do-able to go from 6 direct to 11? Thanks in advance for any info.
There are HUGE differences between v6 and v11. The best option (IMHO) is to put CF11 on a completely different server, test the site/app thoroughly, fix/modify what needs doing, and go from there.
However, if the client insists on going the upgrade route, the first thing I'd do is ask myself if the client is really worth the trouble they are pushing you into.
If you decide to keep the client, then you should upgrade v6 to v8, v8 to v10, then v10 to v11. That should be sufficient.
Still.. upgrading will be a huge hassle. No matter what.
I mostly agree with WolfShade, but it really depends on the complexity of the application. There are indeed huge differences between v6 and v11, but most of those differences are new features or enhancements to existing ones. Very few tags/functions that were around in v6 have been removed in v11 (although many have been deprecated but not yet removed). Review the release notes for v11 to see what is no longer available, then scan your code to see if the application actually uses any of them.
There may be some subtle syntax differences due to issues that were patched in versions 7-11. But as WolfShade suggested, set up a separate server with CF11 and test the code to see what breaks.