Site Collections vs Sites vs Web Applications

 

Using separate Site Collections for your sites provides several benefits

Pros

• 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

Cons

• 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

Pros

• 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

Cons

• 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

Pros

• 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.

Cons

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

 

Fuentes:http://sp365.co.uk/2012/01/initial-topology-planning-site-collections-vs-subsites/