[openstack-dev] [cinder] [nova] Consistency groups?

Philipp Marek philipp.marek at linbit.com
Mon Nov 17 10:56:23 UTC 2014

Hello Xing,

> Do you have a libvirt volume driver on the Nova side for DRBD?
No, we don't. We'd just use the existing DRBD 9 kernel module to
provide the local block devices.

> Regarding getting consistency group information to the Nova nodes, can 
> you help me understand the steps you need to go through?
> 1. Create a consistency group
> 2. Create a volume and add volume to the group
>    Repeat the above step until all volumes are created and added to the 
>    group
> 3. Attach volume in the group
> 4. Create a snapshot of the consistency group
The question I'm asking right now isn't about snapshots.

> Do you "setup" the volume on the Nova side at step 3?  We currently don't 
> have a group level API that "setup" all volumes in a group.  Is it 
> possible for you to detect whether a volume is in a group or not when 
> attaching one volume and "setup" all volumes in the same group?  
Well, our Cinder driver passes some information to the Nova nodes; within 
that information block we can pass the consistency group (which will be the 
DRBD resource name) as well, to detect that case.

> Otherwise, it sounds like we need to add a group level API for this 
> purpose.
Perhaps just adding a "volume is in consistency group X" data item would be 
enough, too?

Sorry about being so vague; I'm just not familiar enough with all the 
interdependencies from Cinder to Nova.



: Ing. Philipp Marek
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting                 http://www.linbit.com :

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