Re: [Qemu-devel] Re: [PATCH 0/3 v4] Live migration without shared storage

[Paolo Bonzini <pbonzini@redhat.com>]

>>> Hmm. How about something like:
>>>
>>> migrate exec:"rsync file1 file2 ... remote:&&  nc remote port"
>>
>> That can surely work to copy the base files, but it is a task for an
>> upper level like libvirt.  For qemu, copying the copy-on-write data is
>> enough.
>
> I agree that it can be useful to let an upper level component to copy the
> storage
> but you will need a way to synchronize with that layer: 1. qemu -->  upper
> layer:
> vm suspended,no more writes to disk.
> 2. upper layer -->  qemu: storage replication is done.
> I don't see how without it you will have a valid copy of the storage.
>
> However make use of the copy on write data and cut the amount of
> transferred data
> can be done only from inside qemu.

Yes, I understand the reason for this feature.  What I meant was that 
you could use rsync to copy the base files from an upper level 
component, before the actual migration is started and qemu transfers the 
copy-on-write data live.

If Michael was saying instead "why is this needed at all", then you 
answered him.

Paolo