[Qemu-devel] [RFC] Specifying storage devices for live migration

[Qemu-devel] [RFC] Specifying storage devices for live migration

[Avishay Traeger]

Hello all,
Currently there is no way to choose storage devices to be migrated.  There
was some discussion about making the monitor API a bit more flexible, but
the code was never written:
http://lists.gnu.org/archive/html/qemu-devel/2009-11/msg01494.html

So today users can choose only:
1) No storage migrated
2) All disks migrated with fully copy
3) All disks migrated with incremental

I'd like to write the code to allow users to choose which disks to migrate,
and how.  What API would you recommend?  What would break the least amount
of utilities?

Thanks,
Avishay

Re: [Qemu-devel] [RFC] Specifying storage devices for live migration

[Stefan Hajnoczi]

On Wed, Jun 15, 2011 at 12:06 PM, Avishay Traeger <AVISHAY@il.ibm.com> wrote:
>
> Hello all,
> Currently there is no way to choose storage devices to be migrated.  There
> was some discussion about making the monitor API a bit more flexible, but
> the code was never written:
> http://lists.gnu.org/archive/html/qemu-devel/2009-11/msg01494.html

Hmm...2009.  Have you seen this recent thread?

http://lists.gnu.org/archive/html/qemu-devel/2011-05/msg00733.html

Are you planning to extend the block migration API and fix known
issues with block migration?

Stefan

Re: [Qemu-devel] [RFC] Specifying storage devices for live migration

[Avishay Traeger]

Stefan Hajnoczi <stefanha@gmail.com> wrote on 15/06/2011 15:49:12:
> > Hello all,
> > Currently there is no way to choose storage devices to be migrated.
There
> > was some discussion about making the monitor API a bit more flexible,
but
> > the code was never written:
> > http://lists.gnu.org/archive/html/qemu-devel/2009-11/msg01494.html
>
> Hmm...2009.  Have you seen this recent thread?
>
> http://lists.gnu.org/archive/html/qemu-devel/2011-05/msg00733.html
>
> Are you planning to extend the block migration API and fix known
> issues with block migration?
>
> Stefan

This feature (selectively migrating block devices during live migration) is
missing for us right now.  I know it's an old thread, but as far as I know,
this hasn't been fixed.  In the more recent thread I see that there are
thoughts to re-work this code (pre-copy vs. post-copy), but doesn't the
interface need to be fixed anyway?  Where are the known issues with block
migration documented?

Thanks,
Avishay

Re: [Qemu-devel] [RFC] Specifying storage devices for live migration

[Marcelo Tosatti]

On Wed, Jun 15, 2011 at 02:06:21PM +0300, Avishay Traeger wrote:
> 
> Hello all,
> Currently there is no way to choose storage devices to be migrated.  There
> was some discussion about making the monitor API a bit more flexible, but
> the code was never written:
> http://lists.gnu.org/archive/html/qemu-devel/2009-11/msg01494.html
> 
> So today users can choose only:
> 1) No storage migrated
> 2) All disks migrated with fully copy
> 3) All disks migrated with incremental
> 
> I'd like to write the code to allow users to choose which disks to migrate,
> and how.  What API would you recommend?  What would break the least amount
> of utilities?

I'm unaware of any application that makes use of the -b flag, so if
thats true breaking the changing the current syntax is fine. The
one Liran suggests looks alright.

Re: [Qemu-devel] [RFC] Specifying storage devices for live migration

[Marcelo Tosatti]

On Wed, Jun 15, 2011 at 02:22:22PM -0300, Marcelo Tosatti wrote:
> On Wed, Jun 15, 2011 at 02:06:21PM +0300, Avishay Traeger wrote:
> > 
> > Hello all,
> > Currently there is no way to choose storage devices to be migrated.  There
> > was some discussion about making the monitor API a bit more flexible, but
> > the code was never written:
> > http://lists.gnu.org/archive/html/qemu-devel/2009-11/msg01494.html
> > 
> > So today users can choose only:
> > 1) No storage migrated
> > 2) All disks migrated with fully copy
> > 3) All disks migrated with incremental
> > 
> > I'd like to write the code to allow users to choose which disks to migrate,
> > and how.  What API would you recommend?  What would break the least amount
> > of utilities?
> 
> I'm unaware of any application that makes use of the -b flag, so if
> thats true breaking the changing the current syntax is fine. The
> one Liran suggests looks alright.

We also need the same feature, BTW.