I've been using this plugin for a while and recently started using Amazon S3/Cloudfront to store files for download. I put the Cloudfront URL in the "Mirrors" section of each download.
It seems like as soon as I do this, the file is only served from the mirror location. I tested this before and after adding the URL -- when the mirror URL is missing, the local copy is served. When the mirror URL is added, only the mirror copy is served.
Am I misunderstanding the way mirror sites work? I assumed that the file would be served randomly from both the local copy and the mirror sites.
If the file is only going to be served from the mirror sites, why does the plugin require a local copy be uploaded?