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Initial Topology Planning: Site Collections vs Subsites

Should I configure my intranet using a single site collection and multiple sub sites or a use multiple site collections?

There are huge pros and cons for each scenario, all of which should be seriously considered as you plan out your implementation. This choice will directly affect your topology and governance model as well.

To clarify, a site collection is a collection of sub sites, it has at least one sub site, but can have many. A site collection cannot have another site collection under it. A web application has a collection of site collections. Site collections are considered equals in a web application, there is no site collection hierarchy.

Using separate Site Collections for your implementation provides several benefits


  • Unique set of users and permissions
  • Unique and separated content databases are possible, which allow for multiple large (200GB+) sites
  • Unique set of workflows, site content types, site columns
  • Unique quotas
  • All farm services are shared
  • Upgrade to next version can be done in a phase approach


  • No out of the box solution to roll up data from site to site
  • If using separate content databases, increase farm administration tasks to backup each database/site
  • Navigation is tougher, no automatic hierarchy or inheritance between site collections
  • Solution management and deployment is harder as each site collection needs to be activated individually

Using a single site collection with Sub Sites has its share of benefits as well


  • Easier data propagation and collaboration, share data and content from site to site
  • Shared permission management across all sites
  • Single content database makes backing up easier
  • True site hierarchy and navigation


  • Single content database, could be a size issue down the road. MS recommended content database size is 200GB, however you can get away with much more
  • Permission management can get chaotic if the amount of users and sub sites are high
  • Restoring a content database will mean that the entire site is down
  • Potentially longer restore times as the database would be larger
  • When database size limitations are approached, moving a site to a new site collection is possible, however that means a new URL for the end user.

In addition to separating out site collections, you can also consider separating web applications. By using multiple web applications, you can separate site collections as well as other farm features


  • Services like User Profiles, Metadata, Business Data, etc. can be unique per web application
  • Separate authentication methods
  • Use of different security policies and user permissions
  • Other finer details like recycle bin retention, outgoing email server, resource throttling, etc.


  • Each web application uses additional memory
  • IIS management cost increases as each web application is a new website


2/3 – added additional pros and cons from Koen Voster’s comments.
2/16 – rephrased the use of sites to better delinate the differences of site collection and sub sites


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  2. January 23, 2012  15:34 by Michael H Reply

    Would have been nice to see some real world scenarios when one method is preferred over the other as this is an issue I'm dealing with now at my company. We started with a single site collection, using subsites but we're out growing our content database.

    I believe we've settled on a 3 web app model.

    1. Portal
    2. MySites
    3. TeamSites/Project Sites/Department Sites

    On #3 we're going to use site collections for true ownership (site collection admins) and quotas.

    • January 23, 2012  15:42 by David Lozzi Reply

      Hi Michael,

      The scenarios to use each will depend on how your requirements and planning fit into the pros and cons of the above. For some real-world examples

      - Setup an extranet allowing customers to log in and pull reports and info. Setup a site collection per customer, there were plans for close to 15-20GB per customer, so we wanted the option to use new site collections as needed. Another pro was unique permissions, search scopes, navigation.
      - Setup an intranet for 22k employees. Setup as a single site collection. Users were all in AD groups, and there was going to be low contribution from the masses, mainly a self service site (HR, policies, etc). Shared navigation was important. Corp users (contributors) were under 500 users, and were only serving up the masses with read-only info.

      It can be difficult but plan for big, even if it take 5 years to get there, at least you'll be prepared.

    • February 20, 2012  18:04 by Chand Reply


      I am almost thinking the simmilar approach...did you face any issues with this approach.... having the Department Sites on the other Web Application. Ofcourse...we need custom navigation..!

      Any thoughts would be appreciated.

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  4. February 3, 2012  08:22 by Koen Vosters Reply

    Things missing out of the top of my head:

    Cons for single site collection
    - restore of content database will mean that the entire site is down
    - longer restore time
    - when size limitations are approached, migration needs to happen to a new site collection -> new url for the enduser

    Pros for multiple site collections / content databases
    - upgrade to next version can be done in a phase approach

    Cons of using web application separation
    - each web application uses memory
    - IIS management cost increases

    • February 3, 2012  13:39 by David Lozzi Reply

      Thanks for the points! I'll update the list.

  5. February 16, 2012  18:27 by Aaron Hamilton Reply

    Great introduction, although I think you are using the term "site" for both site collection and sub sites in certain places. I think it might be best to use "site collection" explicitly at all times, and the same for "sub site".

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