> Op 25 augustus 2017 om 15:00 schreef Matthew Vernon <m...@sanger.ac.uk>:
> 
> 
> Hi,
> 
> We have a medium-sized (2520 osds, 42 hosts, 88832 pgs, 15PB raw 
> capacity) Jewel cluster (on Ubuntu), and in normal operation, our mon 
> store size is around the 1.2G mark. I've noticed, though, that when 
> doing larger rebalances, they can grow really very large (up to nearly 
> 70G, which is nearly all the rootfs on our mons); when recently adding 
> more osds to the cluster (and consequently increasing pg number by 
> increasing the size of an existing pool) we nearly ran out of disk space 
> on the mons due to their mon stores getting very big.
> 
> Since I imagine having your mons run out of disk mid-rebalance is A Bad 
> Idea, is there a way to estimate how big a mon store might get?
> 

As long as there is at least one PG not active+clean there MONs will keep a 
history of all OSDMaps, this can grow large.

With Kraken en Luminous this has changed, but I haven't seen very large 
clusters yet with that version running, they are all still on Jewel.

With Jewel I've seen MON stores of >200GB when doing a multi-day rebalance with 
2000 OSDs in the system.

Wido

> Thanks,
> 
> Matthew
> 
> 
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