There was, IIRC. I think it was Cobind Linux that had something like this, although I don't think it was at the filesystem level. I could be confusing it with a

There was, IIRC. I think it was Cobind Linux that had something like this, although I don't think it was at the filesystem level. I could be confusing it with another distro, though. This was in the early 2000s.