Re: [sami] First SAMI email in the new year, can we go further? Look forward to your opinions.

> > That does mean that an active VM in one place is migrated "live" (with
> > a short downtime of sub seconds) to another place.
> > This is not a case where the VM shuts down and new one is instantiated
> > (i.e., started from scratch) elsewhere.
> > Isn't this what VM migration means?
> 
> I think so, and there's no doubt it would be helpful to be clearer about
> that going forward.  However, my understanding that while the VM image
> would be moved (craploads of kernel state - file tables, page tables,
> all that crap), network activity would have to be quiesced first.  

That understanding is incorrect - network activity is not quiesced.  A
gratuitous ARP or RARP is issued after the migration, and some inbound
packets may get dropped because they are delivered only to the source
location of the migration.

Thanks,
--David

> -----Original Message-----
> From: sami-bounces@ietf.org [mailto:sami-bounces@ietf.org] On Behalf Of Melinda Shore
> Sent: Thursday, March 01, 2012 11:25 AM
> To: Thomas Narten
> Cc: Yingjie Gu(yingjie); sami@ietf.org
> Subject: Re: [sami] First SAMI email in the new year, can we go further? Look forward to your
> opinions.
> 
> On 3/1/12 7:13 AM, Thomas Narten wrote:
> > That does mean that an active VM in one place is migrated "live" (with
> > a short downtime of sub seconds) to another place.
> > This is not a case where the VM shuts down and new one is instantiated
> > (i.e., started from scratch) elsewhere.
> > Isn't this what VM migration means?
> 
> I think so, and there's no doubt it would be helpful to be clearer about
> that going forward.  However, my understanding that while the VM image
> would be moved (craploads of kernel state - file tables, page tables,
> all that crap), network activity would have to be quiesced first.  It
> sounds to me like it's got much in common with old school supercomputer
> checkpoint/restart.  For whatever it's worth we have to do something
> similar with some mid-range "application availability" (you'll notice
> the absence of the word "high") gizmos, and something along the lines of
> a middlebox state migration tool would seem to have some applicability
> there, too.
> 
> Melinda
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