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<p class="MsoNormal">You can do lazy copy that happens only when volume or snapshot is deleted.<o:p></o:p></p>
<p class="MsoNormal">You will need to have refcount on metadata.<o:p></o:p></p>
<p>-----Original Message-----<br>
From: Li, Xiaoyan [mailto:xiaoyan.li@intel.com] <br>
Sent: Tuesday, December 08, 2015 10:11 PM<br>
To: OpenStack Development Mailing List (not for usage questions) <br>
Subject: [openstack-dev] [cinder] Dependencies of snapshots on volumes<br>
<br>
Hi all, <br>
<br>
Currently when deleting a volume, it checks whether there are snapshots created from it. If yes deletion is prohibited. But it allows to extend the volume, no check whether there are snapshots from it.<br>
<br>
The two behaviors in Cinder are not consistent from my viewpoint. <br>
<br>
In backend storage, their behaviors are same.<br>
For full snapshot, if still in copying progress, both extend and deletion are not allowed. If snapshot copying finishes, both extend and deletion are allowed.<br>
For incremental snapshot, both extend and deletion are not allowed. <br>
<br>
As a result, this raises two concerns here: <br>
1. Let such operations behavior same in Cinder.<br>
2. I prefer to let storage driver decide the dependencies, not in the general core codes.
<br>
<br>
Meanwhile, if we let driver to decide the dependencies, the following changes need to do in Cinder:
<br>
1. When creating a snapshot from volume, it needs copy all metadata of volume to snapshot. Currently it doesn't.
<br>
Any other potential issues please let me know.<br>
<br>
Any input will be appreciated. <br>
<br>
Best wishes<br>
Lisa<br>
<br>
<br>
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