Hi,
If you are running Ceph Luminous or later, use the Ceph Manager Daemon's
Balancer module. (http://docs.ceph.com/docs/luminous/mgr/balancer/).
Otherwise, tweak the OSD weights (not the OSD CRUSH weights) until you
achieve uniformity. (You should be able to get under 1 STDDEV). I
would adjust in small amounts to not overload your cluster.
Example:
ceph osd reweight osd.X y.yyy
On 2018-12-21 14:56, Pardhiv Karri wrote:
> Hi,
>
> We have Ceph clusters which are greater than 1PB. We are using tree
> algorithm. The issue is with the data placement. If the cluster utilization
> percentage is at 65% then some of the OSDs are already above 87%. We had to
> change the near_full ratio to 0.90 to circumvent warnings and to get back the
> Health to OK state.
>
> How can we keep the OSDs utilization to be in sync with cluster utilization
> (both percentages to be close enough) as we want to utilize the cluster to
> the max (above 80%) without unnecessarily adding too many nodes/osd's. Right
> now we are losing close to 400TB of the disk space unused as some OSDs are
> above 87% and some are below 50%. If the above 87% OSDs reach 95% then the
> cluster will have issues. What is the best way to mitigate this issue?
>
> Thanks,
> Pardhiv Karri
>
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