Am Fri, 15 Sep 2017 14:28:49 -0400 schrieb Rich Freeman <ri...@gentoo.org>:
> On Fri, Sep 8, 2017 at 3:16 PM, Kai Krakow <hurikha...@gmail.com> > wrote: > > > > At least in btrfs there's also a caveat that the original extents > > may not actually be split and the split extents share parts of the > > original extent. That means, if you delete the original later, the > > copy will occupy more space than expected until you defragment the > > file: > > True, but keep in mind that this applies in general in btrfs to any > kind of modification to a file. If you modify 1MB in the middle of a > 10GB file on ext4 you end up it taking up 10GB of space. If you do > the same thing in btrfs you'll probably end up with the file taking up > 10.001GB. Since btrfs doesn't overwrite files in-place it will > typically allocate a new extent for the additional 1MB, and the > original content at that position within the file is still on disk in > the original extent. It works a bit like a log-based filesystem in > this regard (which is also effectively copy on write). Good point, this makes sense. I never thought about that. But I guess that btrfs doesn't use 10G sized extents? And I also guess, this is where autodefrag jumps in. -- Regards, Kai Replies to list-only preferred.
