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John GriffithJul 12, 2012 10:32 am 
Subject:[Openstack] Some clarifications about Cinder
From:John Griffith (john@solidfire.com)
Date:Jul 12, 2012 10:32:55 am
List:net.launchpad.lists.openstack

Hi Everyone,

Throughout the email thread regarding how to proceed with cinder/nova-volumes and a number of IRC conversations I thought I should try and clarify a few things about Cinder.

First, it should be clear that Cinder is literally a direct copy of the existing nova-volume code. This was intentional in order to maintain compatibility and provide a 'sane' transition. The goal for Folsom from the very start was clearly stated as providing a functional equivalent and as near compatible version as possible (I won't say 100% because there's always room for interpretation with regard to what compatibility means). There are a number of things that were considered and done to make things better for the community:

1. For the most part it's the same code 2. The usage semantics are the same 3. You can still use novaclient just as you did before 4. You can use euca2ools to the same extent that you did before 5. You can also use the new cinderclient

The only thing we're really changing at this point is that now the volume service is it's own project. This of course means that there is some up front configuration regarding a different end point etc, but that really is the bulk of it. You'll notice for example that all of the existing devstack tests etc work exactly the same with cinder as they do with nova-volume, we're not suggesting anybody replace nova-volume with an incompatible interface.

I want to be very clear that myself and just about everybody else I've talked with and worked with DO in fact care about compatibility as well as customer impacts. I know one concern is migration, that's something that is critical and if Cinder doesn't have a robust and clean migration mechanism in place by F3 I don't think we would ask anybody to switch from what they already have.

Thanks, John