Hi,

some news, it seem that it's finally stable for me since 1week. (around 0,7ms 
of commit latency average)
 
http://odisoweb1.odiso.net/osdstable.png

The biggest change is the 18/02, where I have finished to rebuild all my osd, 
with 2 osd of 3TB for 1NVME 6TB.

(previously I only have done it on 1 node, so maybe with replication I didn't 
see the benefit)

I have also push bluestore_cache_kv_max to 1G, and keep osd_target_memory to 
default, and disable THP.

Differents buffers seem to be more constant too.  



But clearly, 2 x smaller 3TB osd with 3G osd_target_memory  vs 1 big osd 6TB 
with 6G osd_target_memory have a differents behaviour.
(maybe fragmentation, maybe rocksdb, maybe number of objects in cache, I really 
don't known)





----- Mail original -----
De: "Stefan Kooman" <[email protected]>
À: "Wido den Hollander" <[email protected]>
Cc: "aderumier" <[email protected]>, "Igor Fedotov" <[email protected]>, 
"ceph-users" <[email protected]>, "ceph-devel" 
<[email protected]>
Envoyé: Jeudi 28 Février 2019 21:57:05
Objet: Re: [ceph-users] ceph osd commit latency increase over time, until 
restart

Quoting Wido den Hollander ([email protected]): 

> Just wanted to chime in, I've seen this with Luminous+BlueStore+NVMe 
> OSDs as well. Over time their latency increased until we started to 
> notice I/O-wait inside VMs. 

On a Luminous 12.2.8 cluster with only SSDs we also hit this issue I 
guess. After restarting the OSD servers the latency would drop to normal 
values again. See https://owncloud.kooman.org/s/BpkUc7YM79vhcDj 

Reboots were finished at ~ 19:00. 

Gr. Stefan 

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