I’m working for an international organization and we are planning to move our website on the Drupal 7. At the moment, we have a custom CMS that contains numerous articles, pages and large collection of pdf documents (around 60.000) stored in a database. For pdf documents we are considering development of a custom module that would retrieve data from the old database as the functionality of this part of CMS and website is quite specific, while the content of our articles and pages (without comments) needs to be migrated to the Drupal database.
As explained on this page: http://drupal.org/documentation/migrate several approaches are available for the migration process. My question is which technique to use? Is it possible just to map fields from the old database to the Drupal database? Would this work and what problems we may expect? Is it better to use the database API and import the content to the Drupal using one of the available migration modules?
I would appreciate any help/advice on the migration issues.