[PVE-User] High ceph OSD latency

[Fabrizio Cuseo]

I will check, but the latency in osd tree is for each disk, and i have high latency on all osd; this is why i don't think that the problem is related to one host or disk.


Inviato da iPad

> Il giorno 15/gen/2015, alle ore 13:17, Lindsay Mathieson <lindsay.mathieson at gmail.com> ha scritto:
> 
>> On Thu, 15 Jan 2015 11:25:44 AM Fabrizio Cuseo wrote:
>> What is strange is that on OSD tree I have high latency: tipically Apply
>> latency is between 5 and 25, but commit lattency is between 150 and 300
>> (and sometimes 5/600), with 5/10 op/s and some B/s rd/wr (i have only 3
>> vms, and only 1 is working now, so the cluster is really unloaded).
>> 
>> I am using a pool with 3 copies, and I have increased pg_num to 256 (the
>> default value of 64 is too low); but OSD latency is the same with a
>> different pg_num value.
>> 
>> I have other clusters (similar configuration, using dell 2950, dual ethernet
>> for ceph and proxmox, 4 x OSD with 1Tbyte drive, perc 5i controller), with
>> several vlms, and the commit and apply latency is 1/2ms.
>> 
>> Another cluster (test cluster) with 3 x dell PE860, with only 1 OSD per
>> node, have better latency (10/20 ms).
>> 
>> What can i check ?
> 
> 
> POOMA U, but if you have one drive or controller that is marginal or failing, 
> it can slow down the whole cluster.
> 
> Might be worth while benching individual osd's