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

["Marconi Rivello" <marconirivello@xxxxxxxxx>]

On 8/10/07, Luciano Rocha <strange@xxxxxxxxxxxxx> wrote:

On Fri, Aug 10, 2007 at 02:18:53PM -0300, Marconi Rivello wrote:
> Hi, Luciano.
>
> On 8/10/07, Luciano Rocha <strange@xxxxxxxxxxxxx> wrote:
> >
> > On Fri, Aug 10, 2007 at 12:42:08PM -0300, Marconi Rivello wrote:
> > > Another issue that I described on a previous email (which,
> > unfortunately,
> > > didn't get any replies) is that this downtime increases to more than 20
> > > seconds if I set the domU's memory to 512MB (the maxmem set is 1024MB).
> > I
> > > repeated the test successively, from one side to the other, with mem set
> > to
> > > 512 and 1024, and the result was always the same. Around 3s with mem =
> > > maxmem, and around 24s with mem=512 and maxmem=1024.
> > >
> >
> > You are using the option --live to migrate, aren't you?
>
>
> Yes, I am. :)

Oh. Well, then, could you try without? :)

I could, but what I'm whining :) about is to have a period of unresponsiveness of a couple of seconds, instead of a tenth of a second. If I do a stop-copy-restart migration it will be even longer.

Also, try the reverse. Ping an outside host in the domU.

I will. In fact, I will try all the monitoring suggestions (from you and the others). Inside domU, outside, third machine, ICMP, ARP...

> 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.

That is odd. Is the Dom0 memory the same (ie., fixed)?

> Would you happen to have any ideas on why it behaves like that?

No idea. I might expect a longer migration time for a machine with a
very active working set, but not a much longer downtime. That should be
only a freeze, final sync, and resume on the other side.

--
lfr
0/0

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I would like to thank everyone who contributed with ideas. It was very helpful. Unfortunately, I will be gone for the next week on a training, and will only be able to further investigate when I get back to work. When I do, I will do some more tests and post what I find out or not.

Thanks again,
Marconi.
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