Re: Any chance to get snapshot-aware defragmentation?

["Niccolò Belli" <darkbasic@linuxsystems.it>]

On venerdì 18 maggio 2018 20:33:53 CEST, Austin S. Hemmelgarn wrote:
> With a bit of work, it's possible to handle things sanely.  You 
> can deduplicate data from snapshots, even if they are read-only 
> (you need to pass the `-A` option to duperemove and run it as 
> root), so it's perfectly reasonable to only defrag the main 
> subvolume, and then deduplicate the snapshots against that (so 
> that they end up all being reflinks to the main subvolume).  Of 
> course, this won't work if you're short on space, but if you're 
> dealing with snapshots, you should have enough space that this 
> will work (because even without defrag, it's fully possible for 
> something to cause the snapshots to suddenly take up a lot more 
> space).

Been there, tried that. Unfortunately even if I skip the defreg a simple

duperemove -drhA --dedupe-options=noblock --hashfile=rootfs.hash rootfs

is going to eat more space than it was previously available (probably due 
to autodefrag?).

Niccolò