Re: [Xen-devel] A migration framework for external devices

["Mike D. Day" <ncmike@xxxxxxxxxx>]

Stefan Berger wrote:
> It should be possible to do that as long as it is definable what 'good 
> state' means.
Yes, good point. In this case the framework should not define policy, 
but the plugin should. In other words, the plugin could do whatever it 
wants to on the target, the framework only cares about the status 
returned by the plugin. If the plugin says "ok to proceed" then the 
migration continues.
> Another question is whether an extensible protocol exists that could be 
> recycled for this purpose or we have to build something from ground up.
Unfortunately the best thing I can think of is a protocol defined using 
xml. As you mentioned, this idea includes existing bulk transfer but 
adds event and procedural semantics. xml encodings are already defined 
for everything we need including bulk data transfers, event semantics, 
and remote procedure calls. However, I don't think we should use xml 
encodings for bulk data transfer. We could keep that part as it is now.
I don't think xml would dominate the migration protocol. We could use it 
for the plugin semantics and to control the important checkpoints in pre 
and post -migration phases. But the migration itself should be encoded 
in the existing file transfer protocol.
Mike


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