[virt-tools-list] Help with live migration (w/o shared storage)

[Eric Blake]

On 02/06/2012 02:59 PM, Gabriel L. Somlo wrote:
> One host is my desktop, the other is a remote machine. I don't
> share any storage between the two hosts, so I worked out that I
> need '--copy-storage-all'.
> 
> My current command line is
> 
> 	virsh -c qemu:///system migrate --live --copy-storage-all \
>               my_test_vm qemu+ssh://root@remote.host.example.com/system
> 
> The error message I get is:
> 
> 	error: Unable to allow access for disk path
> 	/var/lib/libvirt/images/my_test_vm.img: No such file or directory

That means that on the destination, you have to pre-create
/var/lib/libvirt/images/my_test_vm.img prior to calling the virsh
migrate command.  Yes, libvirt should be taught how to make
--copy-storage-all nicer to use, and pre-create files on users behalf,
but no one has submitted a patch for that so far.

> 
> (regardless if I use '--live' or not, BTW).
> 
> I also tried migrating while connected both locally and to the remote
> host from virt-manager, but
> 
> 1. I couldn't find any way to specify or select the equivalent
>    of '--copy-storage-all'

Alas, you'll find that --copy-storage-all isn't very widely tested, and
virt-manager does not support it yet (patches welcome, though).

> 
> and
> 
> 2. I keep getting a similar error after I click 'migrate':
> 
> 	Unable to migrate guest: Unable to allow access for disk path
> 	/var/lib/libvirt/images/my_test_vm.img: No such file or directory

Without --copy-storage-all (which is what virt-manager is doing), then
you have to have shared storage between the two hosts before you can
attempt a migration.

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

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