Re: OSD swapping on Pacific

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Afaik the swapping behavior is controlled by the kernel, there might be some tweaks on the container engine side, but
you might want to try to tweak the default behavior by lowering the 'vm.swapiness' of the kernel:

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/performance_tuning_guide/s-memory-tunables



On 08/16 13:14, Alexander Sporleder wrote:
> Hello list! 
> We have a containerized Pacific (16.2.5) Cluster running CentOS 8.4 and after a few weeks the OSDs start to use swap
> quite a lot despite free memory. The host has 196 GB of memory and 24 OSDs. "OSD Memory Target" is set to 6 GB. 
> 
> 
> 
> $ cat /proc/meminfo 
> MemTotal:       196426616 kB
> MemFree:        11675608 kB
> MemAvailable:   48940232 kB
> Buffers:        46757632 kB
> Cached:           653216 kB
> ....
> 
> 
> $ smem -k
> Command                        		 Swap      USS      PSS      RSS 
> ceph     /usr/bin/ceph-osd -n osd.22     1.7G     3.7G     3.7G     3.7G 
> ceph     /usr/bin/ceph-osd -n osd.10   853.4M     4.6G     4.6G     4.6G 
> ceph     /usr/bin/ceph-osd -n osd.12   793.6M     4.6G     4.6G     4.6G 
> ceph     /usr/bin/ceph-osd -n osd.92   561.3M     4.7G     4.7G     4.7G 
> ceph     /usr/bin/ceph-osd -n osd.14   647.2M     4.9G     4.9G     4.9G 
> ceph     /usr/bin/ceph-osd -n osd.15   567.8M     5.0G     5.0G     5.0G
> ....
> 
> 
> Is that a known behavior, an bug or configuration problem? On two hosts I turned of swap and the OSDs a running happily
> now for more the 6 weeks. 
> 
> Bets,
> Alex
> 
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