Pixelfed currently supports not only local and S3 media storage filesystems, but also 2 fallback S3 disks and a backup disk.

This means you can configure your primary S3 disk using AWS S3 and also have two different fallback disks (say DO Spaces and Wasabi) configured to fallback to in the event the primary disk is unavailable.

You can also configure the backup disk to store app, database, local media backups or full backups on a separate disk/S3 provider!