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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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