Re: [Xen-users] Live migration-delay in gratuitous arp

[Jamon Camisso <jamonation@xxxxxxxxx>]

On 1/11/2011 9:51 PM, Virajith Jalaparti wrote:
> Hi,
>
> I was trying to perform live migration with a VM on a LAN and measure
> the downtime seen by an application (e.g. ping), the time for which the
> application cannot communicate with the VM. The application is run on a
> machine different from those between which the VM is migrated. I noticed
> that the VM remains unreachable for nearly 1-1.5sec. However the
> xend.log file says that the time (the delta) for the last round of the
> migration is around 100msec. So, the VM is actually paused for just
> around 100msec but the application cannot reach it for 1-1.5sec. I
> believe this is because of the delay in the gratuitous ARP being sent.
> Is the implementation such that the ARP is not sent immediately after
> the migration is finished? Is there an easy tweak (without modifying
> source code) by which I can correct this or do I have to modify the
> source code?
>
> I am using Xen from the repos of CentOS 5.5 on a 64bit machine.
I'd be interested to hear if running arping in screen during migration 
on your domU has any effect.
Jamon

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