We just had a fairly extensive discussion about this on the thread "running Qemu / Hypervisor AND Ceph on the same nodes". Check that out in the archives.
On Fri, Apr 3, 2015 at 6:08 AM, Piotr Wachowicz <piotr.wachowicz@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Hey,
>
> We keep hearing that running Hypervisors (KVM) on the OSD nodes is a bad idea. But why exactly is that the case?
>
> In our usecase, under normal operations our VMs use relatively low amounts of CPU resources. So are the OSD services, so why not combine them? (We use ceph for openstack volume/images storage, 7 shared OSD/KVM nodes, 2 pools, 128 PGs per pool, 2 OSDs per node, 10GigE)
>
> I know that during recovery the OSD memory usage spikes. So I guess that might be one of the reasons.
>
> But are there any other concrete examples of situations when the hypervisor could compete for CPU/mem resources with the OSD services running on the same node in a way which would noticeably impact the performance of either?
>
> Kind Regards,
> Piotr
>
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
On Fri, Apr 3, 2015 at 6:08 AM, Piotr Wachowicz <piotr.wachowicz@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Hey,
>
> We keep hearing that running Hypervisors (KVM) on the OSD nodes is a bad idea. But why exactly is that the case?
>
> In our usecase, under normal operations our VMs use relatively low amounts of CPU resources. So are the OSD services, so why not combine them? (We use ceph for openstack volume/images storage, 7 shared OSD/KVM nodes, 2 pools, 128 PGs per pool, 2 OSDs per node, 10GigE)
>
> I know that during recovery the OSD memory usage spikes. So I guess that might be one of the reasons.
>
> But are there any other concrete examples of situations when the hypervisor could compete for CPU/mem resources with the OSD services running on the same node in a way which would noticeably impact the performance of either?
>
> Kind Regards,
> Piotr
>
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
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