I bought a new 250GB Samsung 850 EVO SSD for my laptop that I want to use as primary storage device, together with the old but still functioning 250GB 7500 RPM HDD that I put in the former DVD bay with an adapter caddy.
Right now the HDD has only one big ext4 partition containing the OS, the applications and data files. I want to use the HDD for storing data, but I don't want to miss out on the opportunity to get the speed improvement of the SSD by doing so.
I want to combine say a 50GB or even smaller partition on the SSD and merge it with the partition on the HDD so that the least modified of the most accessed files are automatically moved to the SSD.
- The space occupied by the cache partition is subtracted from the amount of space available.
- The cache speeds up access to the most accessed files regardless of whether they're also the least often modified, which goes against the objective of not wanting to wear out the SSD.
Is the above correct, or could a cache (which one of those two?) help me reach my goal? If the above is correct, do you know of any other viable solution?
Would a union filesystem, like OverlayFS, be helpful here? If you monitored the HDD for the most accessed files (keeping track of their
atime on a daily basis) and identified the least modified ones among them (keeping track of their
mtime), in theory you could move those files to the SSD, freeing space on the HDD, while the union filesystem could make all that transparent to the user.
Would this work?