What do each of the knowledge services (knowledge builder and knowledge base) do?
The knowledge services have the following functions:
Knowledge Builder is used for updating Verity - every time a new entry is added to the queue the builder service gets Verity to add the data or start a re-build.
Knowledge Base service does not communicate with Verity at all. It is used to schedule the builds as per the configuration for the scheduling. In addition, it changes the status of Articles that have past their expiry date to Created so that the Knowledge Administrator can review and re-add the articles if necessary.
You may only want to run the knowledge builder service if you will only manually run builds yourself and you do not use the expiry date on articles. Regular builds should not be required once you have built your collection once because all subsequent data changes (such as adding new incidents if incidents are in your build) will be built in automatically as long as the knowledge builder service is running.