@girish This makes a ton of sense, although I'm not quite sure if I'm doing it right. Under what you linked to, the section should be under the Resources tab, although I think it's moved to the Storage tab (no problems with that, I just wanted to make sure I'm handling it correctly).
The part that's a little confusing is how 'App Data' and Volumes tie together in storage (now it seems this may be resolved as you said, since your working on Volume updating at some point in the future).
Anyways, App Data says to mount an external EXT4 disk, which I assume is done with the 'Mounts' interface right below it. However, the mount says that you are mounting 'Volumes'.
The documentation says 'App Data' is backed up. However, the documentation also says that 'Volumes' are not backed up. So that does leave me a little perplexed as to whether the data will be backed up or not. I think according to your comment, that it will be backed up (because you did say it would no matter where it is on the server). But I just thought I'd check 🙂
In any case, thanks for your help, and hope you have an awesome rest of your week.