What are the Configuration Manager Sites types

Configuration Manager types of Sites

A site consists of a site server, site system(s), site system roles, clients, and resources. There are three types of Configuration Manager 2012 sites.

Server	Purpose	More information
Central administration site - CAS (Optional – always consider if a CAS is necessary if you planned multiple sites)	The recommended location for all administration and reporting for the hierarchy.	SQL Server is required. Does not process client data. Does not support client assignment. Not all site system roles are available. Participates in database replication Can support up to 25 child primary sites. When using SQL Server Enterprise or Datacenter for the site database at the central administration site, the shared database and hierarchy supports up to 400,000 clients. The maximum number of supported clients per hierarchy depends on the SQL Server edition in the central administration site, and is independent of the SQL Server edition at primary or secondary sites. When using SQL Server Standard for the site database at the central administration site, the shared database and hierarchy supports up to 50,000 clients. This is because of how the database is partitioned.
Primary site	A required site that manages clients in well-connected networks. All clients are assigned to a primary site.	SQL Server is required. Additional primary sites provide support for a higher number of clients. Cannot be tiered below other primary sites. Participates in database replication. Each primary site can support up to 250 secondary sites A stand-alone primary site always supports up to 100,000 clients. A child primary site that uses SQL Server installed on the same computer as the site server can support up to 50,000 clients. When using SQL Server that is installed on a computer that is remote from the site server, the child primary site can support up to 100,000 clients. This is true both for Standard and Enterprise Edition of SQL Server.
Secondary site (Optional – Always consider if needed, maybe extra DPs in Primary site is suitable instead)	Manages clients in remote locations	SQL Server Express or a full instance of SQL Server is required. If neither is installed when the site is installed, SQL Server Express is automatically installed. A management point and distribution point are automatically deployed when the site is installed. Secondary sites must be direct child sites below a primary site, but can be configured to send content to other secondary sites. Participates in database replication Each secondary site can support communications from up to 5,000 clients when using a secondary site server computer with the recommended hardware and that has a fast and reliable network connection to its primary parent site.