On 2/28/19 2:59 AM, Glen Baars wrote:
> Hello Ceph Users,
>
> Has anyone found a way to improve the speed of the rbd du command on large
> rbd images? I have object map and fast diff enabled - no invalid flags on the
> image or it's snapshots.
>
> We recently upgraded our Ubuntu 16.04 KVM servers for Cloudstack to Ubuntu
> 18.04. The upgrades libvirt to version 4. When libvirt 4 adds an rbd pool it
> discovers all images in the pool and tries to get their disk usage. We are
> seeing a 50TB image take 25min. The pool has over 300TB of images in it and
> takes hours for libvirt to start.
>
This is actually a pretty bad thing imho. As a lot of images people will
be using do not have fast-diff enabled (images from the past) and that
will kill their performance.
Isn't there a way to turn this off in libvirt?
Wido
> We can replicate the issue without libvirt by just running a rbd du on the
> large images. The limiting factor is the cpu on the rbd du command, it uses
> 100% of a single core.
>
> Our cluster is completely bluestore/mimic 13.2.4. 168 OSDs, 12 Ubuntu 16.04
> hosts.
>
> Kind regards,
> Glen Baars
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