openstack-volume team mailing list archive

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

Hi, thank you for playing around with snapshot.

My bet is to let each volume driver choose which behavior it wants.
i.e. LVM driver chose 1. (At least, my intension was 1. But there would be a bug)
     your driver will choose 3.

thanks,

On Mon, Nov 14, 2011 at 06:18:41PM +0000, Leahy, Oliver wrote:
>     Hi,
> 
>  
> 
>     I reported bug #888649 on the Nova launchpad last week. Briefly, when a
> 
>     snapshot is created on a volume, and the volume is deleted, then the
> 
>     snapshot can never be deleted.
> 
>  
> 
>     Obviously that behavior is broken, so we're looking at fixing it in our
> 
>     volumes implementation. But we want to make sure that the behavior for our
> 
>     volumes and LVM based volumes is as far as possible the same, or if there
> 
>     are differences that they are necessary and logical.
> 
>  
> 
>     We can see three alternatives when nova-volumes receives a request to
> 
>     delete a volume that has been snapshotted :
> 
>  
> 
>     1. Block deletion of a volume if it is being referenced by a snapshot.
> 
>     2. Delete any snapshots referencing the volume and then delete the volume.
> 
>     3. Delete the volume and allow the snap shot to be deleted in the future.
> 
>  
> 
>  
> 
>     I think our preference is for option number 3 because our snapshots can
> 
>     exist happily after the source volume has been deleted. But I understand
> 
>     that this is not the case for LVM based volumes.
> 
>  
> 
>     Given this, what I propose doing is to have our volumes delete the volume
> 
>     and leave the snapshot available, and update the LVM code to block the
> 
>     deletion of a volume if it is being referenced by any snapshots.
> 
>  
> 
>     Is this the best way to proceed with this issue?
> 
>  
> 
>  
> 

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-- 
yamahata