Enable users to create and manage their own 'groups'. Each group can have subscribers, and maintains a group home page where subscribers communicate amongst themselves. They do so by posting the usual node types: blog, story, page, etc. A block is shown on the group home page which facilitates these posts. The block also provides summary information about the group.
Multisite installation in drupal
Multi-site is a very powerful feature in large sites or hosting operations but is often mis-understood. Multi-site is designed as a way to share the same code base for multiple different Drupal based sites. These sites are separate and do not share content or administration. Multi-site just helps with managing the code base, shared themes and modules.
A single Drupal installation can host several Drupal-powered sites, each with its own individual configuration.
Comparison of OG and a Multi site configuration for some parameters:
Speed and Performance of individual sites
Multisite: Very good
OG: Need to cache queries to improve performance
Size of database
Multisite: No of tables in the Database incremental by the number of site specific tables. (Drupal allows for some tables to be shared across sites, hlep us configure common functionality if any.)
OG: Incremental only by an entry in the node table for each of the of content created,and an entry in the group – node access mapping table.
Multisite:Changes in database has to be done across each of the site specific tables - This will be a challenge
OG: Easier to manage change, as all tables are shared.
The concept of OG is good for inter-related sites, when there are a lot of common functionalities across these sites.The decision of Multisite vs OG has to be based on the no of multisites that need to be created and the functionlaities across these sites.
No of sites using OG: