Open Stack

On Mar 25, 2014, at 12:11 PM, Kurt Griffiths <kurt.griffiths at rackspace.com> wrote:

>> As a quick review, storage policies allow objects to be stored across a
>> particular subset of hardware...and with a particular storage algorithm
> 
> Having worked on backup software in the past, this sounds interesting. :D
> 
> What is the scope of these policies? Are they per-object, per-container,
> and/or per-project? Or do they not work like that?

A storage policy is set on a container when it is created. So, for example, create your "photos" container with a global 3-replica scheme and also a "thumbnails-west" with 2 replicas in your West Coast region and "thumbnails-east" with 2 replicas in your East Coast region. Then make a container for "server-backups" that is erasure coded and stored in the EU. And all of that is stored and managed in the same logical Swift cluster.

So you can see that this feature set gives deployers and users a ton of flexibility.

How will storage policies be exposed? I'm glad you asked... A deployer (ie the cluster operator) will configure the storage policies (including which is the default). At that point, an end-user can create containers with a particular storage policy and start saving objects there. What about automatically moving data between storage policies? This is something that is explicitly not in scope for this set of work. Maybe someday, but in the meantime, I fully expect the Swift ecosystem to create and support tools to help manage data lifecycle management. For now, that doesn't belong in Swift.

--John


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