I know at work, we have multiple tiers of data spread over Pure Storage which are all SSD arrays and various other storage solutions which consist of spinning disk. These tiers are based on file accessed date or modified date. I forget which one. So older data gets pushed to slower disks and remote data centers with free space depending on how old the data is. I forget the details because I'm no longer on the team that worked with the storage team but I just wanted to throw that out there as a way to determine what goes into different tiers of storage. That's all in an enterprise environment with multiple data centers across the country with over 100k employees but the same concept could be used in a home environment. New files under a given age would stay on tier 1 which could be SSD's, then moved to local spinning disks between an older age range, and then moved to cloud drives or remote shares after another given age.