<font size=2 face="sans-serif">Adding an ability to Add/Remove existing
volumes to/from CG looks fine. But, it does not help the use-case where
one would want to directly delete a volume from CG.</font>
<br><font size=2 face="sans-serif">Why do we force him to first remove
a volume from CG and then delete?</font>
<br><font size=2 face="sans-serif">As CG goes along with replication and
backends creating a separate pool per CG, removing a volume from CG, just
to be able to delete it in the next step, may be an unnecessary expensive
operation.</font>
<br>
<br><font size=2 face="sans-serif">I think, we can allow removing volume
from a CG with something like '--force' option, so that user consciously
makes that decision.</font>
<br>
<br><font size=2 face="sans-serif">In fact, I think whatever decision user
takes, even to delete a normal volume, is treated as his conscious decision.</font>
<br>
<br><font size=2 face="sans-serif">Thanks,</font>
<br><font size=2 face="sans-serif">Nilesh</font>
<br>
<br>
<br>
<br><font size=1 color=#5f5f5f face="sans-serif">From:
</font><font size=1 face="sans-serif">"yang, xing"
<xing.yang@emc.com></font>
<br><font size=1 color=#5f5f5f face="sans-serif">To:
</font><font size=1 face="sans-serif">"OpenStack Development
Mailing List (not for usage questions)" <openstack-dev@lists.openstack.org></font>
<br><font size=1 color=#5f5f5f face="sans-serif">Date:
</font><font size=1 face="sans-serif">02/07/2015 01:54 AM</font>
<br><font size=1 color=#5f5f5f face="sans-serif">Subject:
</font><font size=1 face="sans-serif">Re: [openstack-dev]
[cinder] Why not allow deleting volume from a CG ?</font>
<br>
<hr noshade>
<br>
<br>
<br><tt><font size=2>As Mike said, allowing deletion of a single volume
from a CG is error prone. User could be deleting a single volume
without knowing that it is part of a CG. The new Modify CG feature
for Kilo allows you to remove a volume from CG and you can delete it as
a separate operation. When user removes a volume from a CG, at least
he/she is making a conscious decision knowing that the volume is currently
part of the CG.<br>
<br>
Thanks,<br>
Xing<br>
<br>
<br>
-----Original Message-----<br>
From: Mike Perez [</font></tt><a href=mailto:thingee@gmail.com><tt><font size=2>mailto:thingee@gmail.com</font></tt></a><tt><font size=2>]
<br>
Sent: Friday, February 06, 2015 1:47 PM<br>
To: OpenStack Development Mailing List (not for usage questions)<br>
Subject: Re: [openstack-dev] [cinder] Why not allow deleting volume from
a CG ?<br>
<br>
On 15:51 Fri 06 Feb , Nilesh P Bhosale wrote:<br>
<snip><br>
> I understand this is as per design, but curious to understand logic
<br>
> behind this.<br>
<snip><br>
> Why not allow deletion of volumes form the CG? at least when there
are <br>
> no dependent snapshots.<br>
<br>
>From the review [1], this is because allowing a volume that's part of a
consistency group to be deleted is error prone for both the user and the
storage backend. It assumes the storage backend will register the volume
not being part of the consistency group. It also assumes the user is keeping
tracking of what's part of a consistency group.<br>
<br>
> With the current implementation, only way to delete the volume is
to <br>
> delete the complete CG, deleting all the volumes in that, which I
feel <br>
> is not right.<br>
<br>
The plan in Kilo is to allow adding/removing volumes from a consistency
group [2][3]. The user now has to explicitly remove the volume from a consistency
group, which in my opinion is better than implicit with delete.<br>
<br>
I'm open to rediscussing this issue with vendors and seeing about making
sure things in the backend to be cleaned up properly, but I think this
solution helps prevent the issue for both users and backends.<br>
<br>
[1] - </font></tt><a href=https://review.openstack.org/#/c/149095/><tt><font size=2>https://review.openstack.org/#/c/149095/</font></tt></a><tt><font size=2><br>
[2] - </font></tt><a href="https://blueprints.launchpad.net/cinder/+spec/consistency-groups-kilo-update"><tt><font size=2>https://blueprints.launchpad.net/cinder/+spec/consistency-groups-kilo-update</font></tt></a><tt><font size=2><br>
[3] - </font></tt><a href=https://review.openstack.org/#/c/144561/><tt><font size=2>https://review.openstack.org/#/c/144561/</font></tt></a><tt><font size=2><br>
<br>
--<br>
Mike Perez<br>
<br>
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