When you are using custom storage to store files, files are uploaded to Uploadcare storge first, and then you have to issue copy requests via our REST API or enable the “auto-copy” option in project settings.
When you are using backup, all your files are stored in Uploadcare storage, and from Uploadcare storage are backed up to your custom storage. If you are using Uploadcare storage, there is no need to issue any kind of requests. Uploadcare storage and backup work simultaneously.
For more information, see