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 <sage@xxxxxxxxxxxx> 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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