Versionable content in Drupal has always suffered from inefficient storage. Each new revision of a content item (historically a "node", but now anything that's fieldable, an "entity") is stored in its entirety in the database. For sites with lot of content, and continuous updates (new revisions) of that content, the database size can grow extremely large over time. This becomes a serious problem for maintenance and disk usage.
The Schema module, which I am now maintaining, lets you compare your actual database tables against the schema that your database is supposed to match. It's a useful tool that tells you when you've got extra tables (say from a previous version of Drupal), missing tables (that were mistakenly or maliciously dropped) or mismatched tables, ones whose implementations do not match their definitions.
I've recently added a feature which provides these lists through Drush for use on the command line or in scripts.
