[openstack-dev] [nova] Feature about QEMU Assisted online-extend volume
zhangleiqiang at huawei.com
Sat Mar 29 02:49:19 UTC 2014
Thanks for your advice.
About the "summit session" you mentioned, what things can I do for it ?
> -----Original Message-----
> From: Duncan Thomas [mailto:duncan.thomas at gmail.com]
> Sent: Friday, March 28, 2014 12:43 AM
> To: OpenStack Development Mailing List (not for usage questions)
> Subject: Re: [openstack-dev] [nova] Feature about QEMU Assisted
> online-extend volume
> It sounds like a useful feature, and there are a growing number of touch points
> for libvirt assisted cinder features. A summit session to discuss how that
> interface should work (hopefully get a few nova folks there as well, the
> interface has two ends) might be a good idea
> On 27 March 2014 16:15, Trump.Zhang <zhangleiqiang at gmail.com> wrote:
> > Online-extend volume feature aims to extend a cinder volume which is
> > in-use, and make the corresponding disk in instance extend without
> > stop the instance.
> > The background is that, John Griffith has proposed a BP () aimed to
> > provide an cinder extension to enable extend of in-use/attached volumes.
> > After discussing with Paul Marshall, the assignee of this BP, he only
> > focus on OpenVZ driver currently, so I want to take the work of
> > libvirt/qemu based on his current work.
> > A volume can be extended or not is determined by Cinder. However, if
> > we want the capacity of corresponding disk in instance extends, Nova
> > must be involved.
> > Libvirt provides "block_resize" interface for this situation. For
> > QEMU, the internal workflow for block_resize as follows:
> > 1) Drain all IO of this disk from instance
> > 2) If the backend of disk is a normal file, such as raw, qcow2, etc,
> > qemu will do the *extend* work
> > 3) If the backend of disk is block device, qemu will first judge if
> > there is enough free space on the device, if only so, it will do the *extend*
> > So I think the "online-extend" volume will need QEMU Assisted, which
> > is simlar to BP .
> > Do you think we should introduce this feature?
> > 
> > https://blueprints.launchpad.net/cinder/+spec/inuse-extend-volume-exte
> > nsion 
> > https://blueprints.launchpad.net/nova/+spec/qemu-assisted-snapshots
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> Duncan Thomas
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