Re: Question on Fragmentations

[Peter Koczan <pjkoczan(at)gmail(dot)com>]

Michael Monnerie wrote:
> On Freitag, 9. Februar 2007 04:08 Peter Koczan wrote:
>   
> > Case in point, I use xfs as the filesystem running under postgres,
> > and after a few days the "major" database clusters showed ~90%
> > fragmentation on their respective partitions (which is about a 10 to
> > 1 ratio of file fragments to files). After running a defragmenter
> >     
>
> Does xfs have such stats, and defragmenter included? It could be a good 
> idea for me to use that, then. Currently I use reiserfs.
>
> mfg zmi
>   
xfs comes with It does have built-in, xfs-approved utilities for stats 
and defragmenting built-in.

xfs_db gives stats (for fragmentation use xfs_db -c frag -r /dev/XXX). 
This works even if the filesystem is mounted and active, but I believe 
that old stats are cached until said filesystem is remounted or until 
some stat collection process runs.

xfs_fsr is the defragmenter (simply use xfs_fsr /dev/XXX). It's safe to 
run this on an active filesystem/database partition, because it throws 
away the fragmented data if files are changed. So, for full 
defragmentation, you'll either want to run it offline, unmounted, or 
during idle times.

Peter