Hello All ... we want to migrate our sites current forum (proprietary built) to a newer, more modern (feature rich) platform. I've been looking around at the available options and have narrowed it down to vBulletin, Vanilla or Phorum (unless you have another suggestion ?). I hope someone here can give me some feedback on their experiences either migrating to a new forum or working deeply with one.

The current forum we have has approx 2.2 million threads in it and is contained in a MySQL database. Data Migration is obviously the first issue, is one of the major Forum vendors better or worse in this regard ?

The software needs to be able to be clustered and cached to ensure availability and performance.

We want it to be PHP based and store it's data in MySQL.

The code needs to be open to allow us to highly customise the software both to strip out a lot of stuff and be able to integrate our sites features. A lot of the forums I've looked at have a lot of duplicate features to our main site, in particular member management, profiles etc. I realise we'll have to do a good bit of development in removing these and tieing it all back to the main site so we want to find a platform that makes this kind of integration as easy as possible.

Finally I guess if 'future proofing' the forum (as best as possible) given the above. Which platform will allow us to customise it but also allow us to keep instep with upgrades. Which forum software has the best track record for bringing online new features in a timely manner ? etc. etc.

I know it's a big question but if anyone here has any experience in some or all of the above I'd be very grateful.