Re: [Xen-users] Live migration: 2500ms downtime

[Tom Brown <tbrown@xxxxxxxxxxxxx>]

On Fri, 10 Aug 2007, Marconi Rivello wrote:

> Yes, I am. :)
> Even if I weren't, it would make sense to expect a lower downtime (or the
> same downtime) by reducing the domU memory. But it takes longer if I reduce
> the domU's memory.
>
> Would you happen to have any ideas on why it behaves like that?
That might indicate a memory crunch... e.g. memory is actively being 
cycled for disk caching... and since it is being changed, XEN is
having to cycle more often whilst trying to sync the memory
maps, I think the xen logs on dom0 may give you some info. But I'm not 
sure if that logic applies to the actual downtime... it certainly will 
apply to the delay between initiating the migrate command and the 
completion.
If the network is still a possible issue, try running the ping from the 
domU being moved and watching _that_ packet stream from the outside via 
tcpdump or something. That might help cut through the bridges/switches ... 
and if it's a bridge/switch issue then you're wasting time trying to fix 
it in XEN (and that would be good to know).
-Tom


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