I have a Ruby on Rails site with models using CarrierWave for file handling, currently using local storage. I want to start using cloud storage and I need to migrate existing local files to the cloud. I am wondering if anyone can point out a method for doing this?

Bonus points for using a model attribute that would allow me to do this row-by-row in the background without interrupting my site for extended downtime (in other words, some model rows would still have local storage while others used cloud storage).

My first instinct is to create a new uploader for each model that uses cloud storage, so I have two uploaders on each model, then transferring the files from one to the other, setting an attribute to indicate which file should be used until they are all transferred, then removing the old uploader. That seems a little excessive.