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On 04/12/2018 10:25 PM, 李俊波 wrote:
> Hello Nova, Cinder developers,
> 
>  
> 
> I would like to ask you a question concerns a Cinder patch [1].
> 
>  
> 
> In this patch, it mentioned that RBD features were incompatible with
> multi-attach, which disabled multi-attach for RBD. I would like to know
> which RBD features that are incompatible?
> 
>  
> 
> In the Bug [2], yao ning also raised this question, and in his envrionment,
> it proved that they did not find ant problems when enable this feature.
> 
>  
> 
> So, I also would like to know which features in ceph will make this feature
> unsafe? 
> 
>  
> 
> [1] https://review.openstack.org/#/c/283695/
> 
> [2] https://bugs.launchpad.net/cinder/+bug/1535815
> 
>  
> 
>  
> 
> Best wishes and Regards
> 
> junboli
> 
>  

Hi,

As noted in the comment in the code [1] -- the exclusive lock feature
must be disabled.  However, this feature is required for RBD mirroring
[2], which will be the basis of Cinder volume replication for RBD.

We are currently prioritizing completing support for replication over
multi-attach for this driver, since there is more demand for that
feature.  After that, we will look more at multi-attach and how to let
deployers choose to enable replication or multi-attach.

[1]
https://git.openstack.org/cgit/openstack/cinder/tree/cinder/volume/drivers/rbd.py?id=d1bae7462e3bc#n485

[2]
http://docs.ceph.com/docs/master/rbd/rbd-mirroring/#enable-image-journaling-support

Thanks,
Eric