Re: XFS defragmentation issue

Dave Chinner
2010-09-11T08:22:59Z

On Sat, Sep 11, 2010 at 07:55:32AM +0100, John Lister wrote:
> Stan Hoeppner wrote on 9/10/2010 14:00
> >>On 10/09/2010 15:41, John Lister wrote:
> >Try unmounting and remounting the filesystem, and see if the various
> >tools all report the same thing afterwards. This solved the exact same
> >problem for me very recently, though I'm on kernel 2.6.34.1 and xfsprogs
> >2.9.8.
>
> Cheers, that got rid of most of it, there is still a slight
> discrepency (50 extra fragments) which I can live with.

xfs_db used buffered IO on the block device, which is not coherent
with the filesystem. If you are using it on an active filesystem,
then running "echo 1 > /proc/sys/vm/drop_caches" before you run
xfs_db should make it read from disk at least once....

Cheers,

Dave.
--
Dave Chinner
david@fromorbit.com