You might just have too much data per PG.  If a single PG can account for
4% of your OSD, then 9% difference in used space on your OSDs is caused by
an OSD having only 2 more PGs than another OSD.  If you do have very large
PGs, increasing your PG count in those pools should improve your data
distribution.

On Mon, Aug 20, 2018 at 3:59 PM Sage Weil <[email protected]> wrote:

> On Mon, 20 Aug 2018, Stefan Priebe - Profihost AG wrote:
> > Hello,
> >
> > since loic seems to have left ceph development and his wunderful crush
> > optimization tool isn'T working anymore i'm trying to get a good
> > distribution with the ceph balancer.
> >
> > Sadly it does not work as good as i want.
> >
> > # ceph osd df | sort -k8
> >
> > show 75 to 83% Usage which is 8% difference which is too much for me.
> > I'm optimization by bytes.
> >
> > # ceph balancer eval
> > current cluster score 0.005420 (lower is better)
> >
> > # ceph balancer eval $OPT_NAME
> > plan spriebe_2018-08-20_19:36 final score 0.005456 (lower is better)
> >
> > I'm unable to optimize further ;-( Is there any chance to optimize
> > further even in case of more rebelancing?
>
> The scoring that the balancer module is doing is currently a hybrid of pg
> count, bytes, and object count.  Picking a single metric might help a bit
> (as those 3 things are not always perfectly aligned).
>
> s
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