Thank you @Alameda for your thoughtful reply.I don’t approach storage the way you do.
I have my System Software, my Applications, and non-media Documents files… and that takes up very little storage…
I think your approach is wrong.
What I suggest is that you break your storage and your backups into two pools. One of the pools contains your System Software, the Applications, and your non-media documents. The other pool contains the media files which, I assume, are likely taking up 7.5 TB of your 8 TB.
For most of us, our media collection does not change, it only grows. In my case, I take thousands of 45 megapixel RAW photos. I have about 4 TB of them... but I keep them separate from my other files, in folders which are excluded from Time Machine backup. In my case, I backup my photos manually to an external SSD, which gets backed up to my NAS.
And my basic system/applications/documents, which still includes some photos and videos but not a lot... that's only about 200 GB and it gets backed up to two separate Time Machine drives. One is direct attached and the other is my NAS.
Managing the backup of a single monolithic 8 or 16 TB volume is a lot. If you don't separate the media files out, then every time your backup software runs a backup, it's going to run through all 8 or 16 TB of stuff to see if any of them have changed... and you know perfectly well that 15 1/2 of that 16 TB isn't going to change ever, because you took the photos of your kid's 6th birthday party ten years ago and you just want to keep it as-is.
I will reread after I start this phone back up. Am taking a vacation day tomorrow to tackle a bunch of this so your reply is perfect timing.