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@lists.ceph.com
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
> 

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