Pitfalls of Site Collection Consolidation

So, you're considering consolidating Site Collections in SharePoint.  I suspect that some of your reasons are:

1. I feel like I have too many site collections.
2. It feels like it's difficult to manage the security of all of my site collections.
3. Publishing based navigation doesn't cross the site collection boundary.
4. We're really only hosting a single "site" in this web application anyway.

What do you loose when you consolidate Site Collections?

• Maximal, you can only have one Content Database per Site Collection.
• More content databases allow for different SQL Server based backup schedules based on the site collection's use.
• Content Databases will be at their smallest (individually) when there's only one Site Collection in each database.
• Content Databases can be distributed across multiple SQL Server instances, distributing the SQL workload across a SQL grid.
• Power Shell & Central Admin based backups all you to backup individual Site Collections.
• If you have one big site collection, your backup is going to be one big file.

What do you gain by consolidating Site Collections?

• Security will be just as difficult.
• If you users are installing no-code solutions (i.e. site templates), they'll need to be site collection admins.  This can get complicated quickly if users become an admin of the entire web app.
• You'll still need to audit the entire hierarchy's ACLs to ensure you're protecting information appropriately.
• Publishing based navigation can be used to navigate everything in your site.
• Granted that your web-sites don't get deeper than your maximum menu depth.  That's typically 2-3 levels based on what you've munged in stock Master Pages.
• With 3rd party solutions for SP2010 and Managed Navigation for SP2013, the problem becomes how important is top-menu security trimming.

What are some gotcha's if you decide to consolidate?

• Depending on the tool you use you need to match Site Collection Features in the Source and Target.
• Many Collection level features install content types and list templates, if these aren't in the target you're going to run into trouble.
• In SP2013 if your going from a Publishing Site to another site, Export-SPWeb and Import-SPWeb won't let you pass unless Publishing Infrastructure is turned on.
• SP2013 Workflows: They may not enable after merging site collections. Scenario:
• Source site collection has some SP2010 workflow remnants, and aren't necessarily in use.
• Destination site didn't have Workflows enabled before the merge.
• After the merge the Workflow feature won't enable because some of the content types are already present, and marked as non-replacable.
• It's really a bug in the installer that it doesn't recognize that these are the same, but it sill won't go.
• Solution: Enable Workflows prior to merging, or you're going to have to re-merge with a site collection where it is enabled, or workflows will be a no-go.

Short story, Site Collection consolidation is something that requires more than a few moments of thought.  Make sure you're doing it for the right reasons, take precautionary steps, and you'll meet with success.