[Openstack-operators] cinder volume_clear=zero makes sense with rbd ?

Serguei Bezverkhi (sbezverk) sbezverk at cisco.com
Thu Nov 5 19:25:05 UTC 2015


With Kilo I noticed that with LVM backend for these two parameters to be considered they must be put in specific LVM section. Like this:


Otherwise they are ignored and it was taking lots of time to delete the volume, I do not use rbd but I suspect it should be done the same way as well.

Thank you


Serguei Bezverkhi,
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From: David Wahlstrom [mailto:david.wahlstrom at gmail.com]
Sent: Wednesday, November 04, 2015 12:53 PM
To: OpenStack Operators <openstack-operators at lists.openstack.org>
Subject: Re: [Openstack-operators] cinder volume_clear=zero makes sense with rbd ?

Looking at the code in master (and ignoring tests), the only drivers I see reference to volume_clear are the LVM and block device drivers:

$ git grep -l volume_clear

So other drivers (netapp, smb, gluster, and of course Ceph/RBD) simply ignore this option (or more accurately, don't take any action).

On Wed, Nov 4, 2015 at 8:52 AM, Chris Friesen <chris.friesen at windriver.com<mailto:chris.friesen at windriver.com>> wrote:
On 11/04/2015 08:46 AM, Saverio Proto wrote:
Hello there,

I am using cinder with rbd, and most volumes are created from glance
images on rbd as well.
Because of ceph features, these volumes are CoW and only blocks
different from the original parent image are really written.

Today I am debugging why in my production system deleting cinder
volumes gets very slow. Looks like the problem happens only at scale,
I can't reproduce it on my small test cluster.

I read all the cinder.conf reference, and I found this default value
=>   volume_clear=0.

Is this parameter evaluated when cinder works with rbd ?

I don't think that's actually used with rbd, since as you say Ceph uses CoW internally.

I believe it's also ignored if you use LVM with thin provisioning.


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David W.
Unix, because every barista in Seattle has an MCSE.
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