Primary Core Driver#One core driver is designated as the primary core driver. Other core drivers are known as secondary core drivers. The primary core driver serves the Web interface and provides environmental information during the installation process for other core drivers. Only the primary core driver listens for events from eDirectory and performs Trawls.
Secondary Core Drivers#Secondary Core Drivers use the same configuration information as their "Primary Core Driver" but allow loads to be spread horizontally. Each core driver will typically handle up to 500 platform receivers and Secondary Core Drivers are how you can go beyond this limitation. Each Secondary Core Driver would be installed on a separate host or at minimum a separate port on the same server as the Primary Core Driver. The Secondary Core Drivers only read the same census as their Primary Core Driver.
Typically the first Core Driver becomes the "Primary" Core Driver. All others are "Secondary".