libvirt users - Aug 2014 - Re: [help] Does "virsh blockpull" works on live virtual machine

Hi all,
I have a kvm virtual machine running (qemu version 2.0), and I had took several
external snapshots of the disk( using "virsh snapshot-create-as").
Now, the existed disk files relationship look like: base <- snap1 <-snap2
<- current using disk file. Now I want to remove snap1 and snap2, and let
current disk using the base image file as back file directly. Unfortunately, for
some reason, I can not shutdown the vm, and exectue the "virsh
blockpull" command. Can I execute the "virsh blockpull" while the
vm is power on, and the application in the vm is not affected?
Thanks very much!
Daniel

On 08/06/2014 06:04 AM, chenyanqiu@keytonecloud.com
wrote:
> Hi all,
[please configure your mailer to wrap long lines]
> ...Now I want to remove snap1 and snap2, and let current disk using the
base image file as back file directly. Unfortunately, for some reason, I
can not shutdown the vm, and exectue the "virsh blockpull" command.
Can
I execute the "virsh blockpull" while the vm is power on, and the
application in the vm is not affected?

Yes, that's the point of the 'virsh blockpull' command - live chain
manipulation with no impact to the running guest.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

Thanks, Eric!
However, I met more problems today. I tried blockpull with an test env. And
virsh command returned an error:
error: failed to query job for disk /test/over_5_1.qcow2
error: internal error: client socket is closed
error: One or more references were leaked after disconnect from the hypervisor
error: Reconnected to the hypervisor

I "qemu-img info" the top image, its back file was already pointed to
the base file.
But the virtual machine process's cpu load was very high in the hypervisor,
and that vm was a "dummy" machine, should not be high loaded.
I don't know whether the pull operation is still going on or not, and what
is the final result.

And one more question hits me. What if the "blockpull" command fails?
will it leave the disk files in unconsistant/corrupt state?
Thank you very much.

Daniel
 
From: Eric Blake
Date: 2014-08-06 21:29
To: chenyanqiu@keytonecloud.com; libvirt-users
Subject: Re: [libvirt-users] [help] Does "virsh blockpull" works on
live virtual machine
On 08/06/2014 06:04 AM, chenyanqiu@keytonecloud.com
wrote:
> Hi all,
 
[please configure your mailer to wrap long lines]
 
> ...Now I want to remove snap1 and snap2, and let current disk using the
base image file as back file directly. Unfortunately, for some reason, I
can not shutdown the vm, and exectue the "virsh blockpull" command.
Can
I execute the "virsh blockpull" while the vm is power on, and the
application in the vm is not affected?
 
Yes, that's the point of the 'virsh blockpull' command - live chain
manipulation with no impact to the running guest.
 
-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org