My question actually consists of multiple questions. I'm frequently reading about companies who deploy a small subset of features for a select amount of customers using the live "database". Ruby on Rails and its ecosystem have deployment tools and database migrations to deploy or rollback such features in a live production or staging environment.

My question, how is this done for an asp.net (mvc in particular) application? How do you test your newly released features against live data? Do you have any tools to modify the existing database and roll back changes if necessary? Do you make backups before deployment?

Update

Maybe I should point out that my question is not really clear, getting more answers here will help me phrase the question better. To make it easier I will describe a situation I'm commonly seeing with some of my clients.

My clients have large deployments of popular web applications. They do not have staging/QA/testing servers. (yes this is not optimal). The data their apps consist of are images, xml files, user uploads and data in Sql Server. Having a few records, of their production database and a couple of dummy files is not a substitute of testing against real data in my opinion. How would you design a workflow that can create a acceptable environment to mimic a production environment before going live?