The Global Catalog (GC) Placement

  • Users who login to the domain need to access the GC to obtain a list of Universal Groups they belong to.
  • If a GC does not exist in the same site, the users will have to obtain this information from a DC at another site.
  • A GC, unlike other DCs, have a ready only copy of all objects in the forest with their commonly used attributes.
  • If you have many domains with a lot of users in each domain – GC replication needs will be a fair bit higher than that of a regular DC.
  • Some applications such as Exchange Servers put a fair bit of load on GCs. GCs should be placed locally in sites hosting these types of applications.
  • Recommended that each site have at least one GC and a 2nd (Depending on size) for resiliency.
  • Typically sites with more than 100 users should have a GC.
  • Provides search capability of any object within a forest
  • All objects from all domains are included in the GC.
  • Only commonly used attributes of the objects are replicated to the GC.
  • GCs can be found by querying for the GC Service Record in DNS (By Site).
  • Resolves User Principal Names (UPNs) to the username.
  • GC Stores user time restrictions and other information to permit/deny logon requests.
  • Partial Attribute Set – you can configure which attributes are included in the GC replication.