Re: ceph IO are interrupted when OSD goes down

[Eugen Block <eblock@xxxxxx>]

Hi,

min_size = k is not the safest option, it should be only used in case  
of disaster recovery. But in this case it's not related to IO  
interruption, it seems. Are some disks utilized around 100% (iostat)  
when this happens?


Zitat von Denis Polom <denispolom@xxxxxxxxx>:

> Hi,
>
> it's
>
> min_size: 10
>
>
> On 10/18/21 14:43, Eugen Block wrote:
> > What is your min_size for the affected pool?
> >
> >
> > Zitat von Denis Polom <denispolom@xxxxxxxxx>:
> >
> > > Hi,
> > >
> > > I have 18 OSD nodes in this cluster. And it does happen even if  
> > > one OSD daemon goes down or flaps.
> > >
> > > Running
> > >
> > > ceph version 15.2.14 (cd3bb7e87a2f62c1b862ff3fd8b1eec13391a5be)  
> > > octopus (stable)
> > >
> > > thx!
> > >
> > >
> > > On 10/18/21 12:12, Eugen Block wrote:
> > > > Hi,
> > > >
> > > > with this EC setup your pool min_size would be 11 (k+1), so in  
> > > > case one host goes down (or several OSDs fail on this host), your  
> > > > clients should not be affected. But as soon as a second host  
> > > > fails you’ll notice IO pause until at least one host has  
> > > > recovered. Do you have more than 12 hosts in this cluster so it  
> > > > could recover one host failure?
> > > >
> > > > Regards,
> > > > Eugen
> > > >
> > > >
> > > > Zitat von Denis Polom <denispolom@xxxxxxxxx>:
> > > >
> > > > > Hi,
> > > > >
> > > > > I have a EC pool with these settings:
> > > > >
> > > > > crush-device-class= crush-failure-domain=host crush-root=default  
> > > > > jerasure-per-chunk-alignment=false k=10 m=2 plugin=jerasure  
> > > > > technique=reed_sol_van w=8
> > > > >
> > > > > and my understanding is if some of the OSDs goes down because of  
> > > > > read error or just flapping due to some reason (mostly read  
> > > > > errors , bad sectors in my case) clients IO shouldn't be  
> > > > > disturbed because we have other object replicas and Ceph sould  
> > > > > manage it. But clients IOs are disturbed, cephfs mount point  
> > > > > gets inaccessible on clients even if they are mounting cephfs  
> > > > > against all 3 monitors.
> > > > >
> > > > > It's not happening always just sometimes. Is it right  
> > > > > understanding that it can happen if read error or flapping  
> > > > > occures  on active OSD?
> > > > >
> > > > >
> > > > > Thx!
> > > > >
> > > > > _______________________________________________
> > > > > ceph-users mailing list -- ceph-users@xxxxxxx
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