[libvirt] Block-migrate

Ruben Kerkhof ruben at rubenkerkhof.com
Fri Aug 13 17:28:25 UTC 2010


Hi Justin,

On Fri, Aug 13, 2010 at 08:53, Justin Clift <jclift at redhat.com> wrote:
> Hi Ruben,
>
> Chris Lalancette was kind enough to look into why libvirt was requiring
> root:root QEMU ownership for tunnelled migration to work.  He found the
> problem (temporary socket file being located in root owned directory) and
> submitted the patch last night.

Perfect, thanks a lot.
>
> The next release of libvirt (0.8.4) should therefore allow qemu:qemu owned
> QEMU to work. :)
>
> Note, I only tested the standard "shared storage" tunnelled migration,
> rather than block migration too.

I've just tested those patches with block-migrate (only the
--copy-storage-all option) and they work fine.

> Personally not sure if there are further
> gotchas in block migration code waiting to be found. ;)

One issue is that during the block-migrate, virsh list simply hangs,
and some python scripts that I'm using which talk to the libvirt api
return with "Timed out during operation: cannot acquire state change
lock".

Haven't looked at the code yet, but I suspect that the block migration
is holding a lock longer than a normal migration on shared storage
would.

The other issue has nothing to do with block migrate, but migration in
general. It's sometimes hard to see if the error message virsh migrate
is returning is generated on the source or the destination side.

>
> Hope that helps.
>
> Regards and best wishes,
>
> Justin Clift
>

Thanks again,

Ruben




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