Just to note the "magic" of object-map... If you had a 50TB RBD with object-map and 100% of the RBD is in use, the rbd rm will take the same amount of time to delete the RBD as if you don't have object-map enabled on a brand new 50TB RBD that has no data in it. Removing that many objects just takes a long time. object-map makes it so that operations like rbd rm will skip objects not in use and speed up the operation.
I had a dev accidentally create a 1EB (exabyte) RBD that would have probably taken months to actually delete. Instead I did what you were talking about and removed the RADOS objects manually for the RBD and then removed the RBD much more quickly.
To directly answer your question about if this speed is expected, I would say yes. Ceph is really good at keeping your data in tact... not so good at deleting it. :)
On Sat, Mar 17, 2018 at 12:18 PM Jack <ceph@xxxxxxxxxxxxxx> wrote:
Yes, this is what object-map does, it tracks used objects
For your 50TB new image:
- Without object-map, rbd rm must interate over every object, find out
that the object does not exists, look after the next object etc
- With object-map, rbd rm get the used objects list, find it empty, and
job is done
For rbd export, this may the the same
However, rbd export exports a full image (so, in your case, 20TB)
You may want to use rbd export-diff (which will still be some kind of
slow without object-map, but will only output usefull data)
Another tip: if you can, consider using rbd-nbd
This allows you to mount a rbd volume using librbd
On 03/17/2018 05:11 PM, shadow_lin wrote:
> Hi list,
> My ceph version is jewel 10.2.10.
> I tired to use rbd rm to remove a 50TB image(without object map because krbd does't support it).It takes about 30mins to just complete about 3%. Is this expected? Is there a way to make it faster?
> I know there are scripts to delete rados objects of the rbd image to make it faster. But is the slowness expected for rbd rm command?
>
> PS: I also encounter very slow rbd export for large rbd image(20TB image but with only a few GB data).Takes hours to completed the export.I guess both are related to object map not enabled, but krbd doesn't support object map feature.
>
>
>
>
> 2018-03-18
>
>
>
> shadowlin
>
>
>
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
>
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