Unfortunately, you won't be able to use the new "rbd feature enable" command 
against a Hammer OSD since the command requires support within the RBD object 
class in the OSD.  Additionally, since your images haven't had the object map 
enabled, they would need to have an object map built prior to that optimization 
actually taking effect.  The master branch has a new "rbd object-map rebuild" 
helper to compute the object map on images that don't currently have a valid 
object map.

It's quite possible that these new features will be backported into Hammer at 
some point in the future.  Therefore, I would recommend waiting for the full 
toolset to become available.

-- 

Jason Dillaman 
Red Hat 
dilla...@redhat.com 
http://www.redhat.com 


----- Original Message -----
From: "Christoph Adomeit" <christoph.adom...@gatworks.de>
To: ceph-users@lists.ceph.com
Sent: Tuesday, April 28, 2015 10:06:12 AM
Subject: [ceph-users] Use object-map Feature on existing rbd images ?

Hi there,

we are using ceph hammer and we have some fully provisioned
images with only little data.

rbd export of a 500 GB rbd Image takes long time although there are only
15 GB of used data, even if the rbd-image is trimmed.

Do you think it is a good idea to enable the object-map feature on
already existing rbd images ?

I am thinking about using the rbd binary from ceph-master to change
the features of some existing rbd images like this:

rbd --image-feature exclusive-lock
rbd --image-feature object-map

Do you think this is a good idea, this will work and will be stable ?

Thanks
  Christoph
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