Re: [Qemu-devel] [PATCH v4 0/6] Efficient VM backup for qemu

[Paolo Bonzini]

Il 22/02/2013 12:13, Dietmar Maurer ha scritto:
> Opening several NBD sockets 'nbd:127.0.0.1:1235' seems dangerous to me. One 
> backup task
> and easily write to the wrong port - there is no protection?

You can also use the named-export support.  Something like

   --nbd=127.0.0.1:1235
   --blockdev=virtio-drive0 --blockdev=virtio-drive1 --blockdev=ide0-hd0

etc.

Then QEMU can migrate to nbd://127.0.0.1:1235/virtio-drive0.

> Or how can we guarantee that only one kvm process can write to that NBD 
> device?

Why is this needed?

BTW, with Kevin's proposal of doing migrate+backup+continue at the
management level, you may not even need extensions to the transaction
command.  It's much easier to implement.

Paolo

> 
>> >   transaction actions=[{'type': 'migrate-async',
>> >                         'destination': 'tcp:127.0.0.1:1234',
>> >                         'id': 'migration'},
>> >                        {'type': 'point-in-time-copy-async',
>> >                         'wait-for': 'migration',
>> >                         'device': 'virtio-drive0',
>> >                         'destination-device': 'nbd:127.0.0.1:1235'}]
>> > 
> 
>