Help with archiving strategy and design


I’m trying to do something with NextCloud and I’m trying to figure out the most appropriate way to do it - it might be that I’m in the wrong place and need to be thinking more with my Linux hat on.

I have a NextCloud server with two 4TB HDD spinners RAIDed in it, one 1TB SSD and one 500Gb SSD. My current storage solution is OneDrive, and I would like to keep that as a ‘oh look, my house is on fire’ backup - although I want to be driving everything through NextCloud outside of a failover.

The 500Gb SSD is for the OS, and currently has the NextCloud data dir on it as /mnt/Store (not a mount, just a folder - am planning on changing that with the below)

I’m storing my day to day docs (think: finances, CV, and once I find a better OneNote replacement my notebook etc) on NextCloud but the bulk of the data is photos, photos which are used regularly after the event and then go a bit stale.

I want to try and use the SSD as a cache, i.e. anything that’s been accessed in the last 6 months exists on the SSD.

I want to try and use the HDD as cold storage, i.e. anything that has not been accessed in the last 6 months exists on the HDD.

I want the HDD to be spun down as much as possible.

As the HDD is much larger than the SSD I would like the things on the SSD to also exist on the HDD.

The HDD is backed up on OneDrive.

Now, one way I could do it is through the linux system, a series of cleverly designed rsync scripts and (maybe) some kind of symlinks could do it all in the filesystem.

However, NextCloud already processes the inbound files and has all the intelligence on them, so it seems that its a better place to do it.

I can code, so if I need to build something, am happy with the that.

A few questions:
a) Am I trying to do something stupid?
b) Should I be trying to do this in NextCloud or the FileSystem?
c) I think I need to build an app with the external-storage app to get this done, is that the best way to do it?
d) Any advice, am I looking at this right?
e) Am I trying to do something stupid?

Anything given is greatly appreciated!