On Sat, Oct 31, 2015 at 10:25 AM, Jeremi Piotrowski <jeremi.piotrow...@gmail.com> wrote: > > This is one of the problems with copy-on-write filesystems - they make > disk space accounting more complicated especially with snapshots.
Indeed, it is one of the problems with copy-on-write anything. Shared memory is a similar situation - do you count glibc in RAM one time or many? It also gets complicated with compression and dynamic mirroring and such, though at least in these cases a better prediction could probably be made than is often done. Free space usage in these cases really needs to distinguish between shared/exclusive space, but in the case of the former it will probably never be easy to display in a concise manner just what you need to do to reclaim that space. Obviously shared space can only be reclaimed if all its references are deleted. The flip-side of this is that copying data is really cheap. Alias cp to cp --reflink=auto and you can use a copy in many situations where you might have previously used a hard/symbolic link. Obviously all three of those do different things, but before I had reflinks I found myself using hard/symbolic links when they were less than ideal. -- Rich
