A secondary site provides the benefits of an SMS site, but without needing a local administrator to run it. A secondary site can be especially helpful when a slow communication link separates a primary site from clients. In such a case, you can configure a server local to those clients as a secondary site.
This approach enables the clients to be managed from a site server on their local area network (LAN). The slow link is then used only when the primary site and secondary site communicate. Clients will experience fast response times because their CAP and distribution point are no longer separated from them by the slow communication link.
Clients won't get an advertisement, for example, any sooner (because the slow link is still used), but when they accept an advertisement they will download the package from the secondary site over their LAN instead of the slow link, so the clients' wait will be brief. This is analagous to viewing web sites stored on a local hard drive after they have been downloaded from the internet over a 28.8 bps modem; the downloading happens in the background while users do something else. Similarly, data trickles between the primary and secondary site while clients are doing something else.
Secondary sites do not have:
Secondary sites can only be installed after at least one primary site has been installed, because secondary sites are managed from a primary site. When you create a secondary site, SMS automatically creates an address for the secondary site on the parent site, and vice versa, but you must still install a sender for the two sites to communicate.
Create a Secondary Site
Upgrade or Reinstall a Secondary Site
Delete a Secondary Site
About Site Hierarchies
Configuring SMS Site Settings Overview
Secondary Site Overview