S3-compatible storage. In my case, Backblaze B2. The idea is to make the backend compatible with rclone, so that one can pick whatever storage they want (including B2 / S3 and others)
I backup my immich photos in B2 with rclone but I prefer having it as a separate process (also, the backup is append-only). I don't need "hyperscale", and storing directly on S3/B2/remotely breaks a bit the 3-2-1 rule I want to follow.
On B2 (and S3 storage in general) you can set a retention policy for what happens after you delete an object (e.g: object lock with persistance for at least 30 days). Of course this is not a substitute for a backup - but it's better than discovering that you deleted your whole 1TB library when it's too late
