I recently upgraded a couple sites using Drupal 4.7 to 6.20. The process was fairly straight forward except for a few things.

The upgrade from 4x to 5x went smoothly.
The upgrade from 5.23 to 6.20 was a disaster.

You have to start with a fresh install of 6.20. If you use your 5.23 directory it will fail.
You have to remove the database connection line in settings.php or 6.20 will assume the database works, and the existing 5.x database schema will fail.

A couple people emailed and thought the piece on NoSQL databases was unfair. Perhaps it was heavier handed than is really justified, as Mohawk Software has its own, albeit out of date, NoSQL system.

MSession was a NoSQL solution built about 10 years ago for handling transient shared data for an MPI compute cluster. It was later adapted to PHP as a shared session management system. After that, it was used as a shared data cache.

There is a lot of discussions about “NoSQL” out there and a lot of developers are spending a lot of time advocating it over more established RDBMS. What is NoSQL? NoSQL is a movement that works on the premise that “relational databases” don't scale to fit the web, and are thus mostly obsolete in the web environment.

My employer has decided to move to a new direction and as such I am not currently actively employed. Now's your chance!! Have any exciting projects that you need done?

contact me markw this domain mohawksoft and org and let me know.