Comment by Mayzie

> I don't know if this exists or not, but I'd like to try something like a fuse filesystem which can transparently copy a file to a fast scratch SSD when it is first accessed.

You may be interested in checking out bcache[1] or bcachefs[2].

[1] https://www.kernel.org/doc/html/latest/admin-guide/bcache.ht...

[2] https://bcachefs.org/