Re: [Xen-users] drbd 8 primary/primary and xen migration on RHEL 5

[Antibozo <xen-users@xxxxxxxxxxxx>]

On 2008-07-31 23:58, nathan@xxxxxxxxxxxx wrote:
> On Thu, 31 Jul 2008, Antibozo wrote:
> > On 2008-07-31 23:24, Antibozo wrote:
> > > One can run a job on the vm to generate a packet every second or two 
> > > to resolve this; ping in a loop should do it.
> > Quick follow-up:
> >
> > arping -b -A *ip-address-of-vm*
> >
> > seems to work pretty well. I get a 2-3 second dropout if I'm running 
> > this during live migration.
> Odd, I am seeing 15 - 20 sec, how on earth does someone get 165ms that 
> is talked about? I get the same delay if I am migrating over gig e or 20 
> gig infiniband. It also should not be my I/O subsystem as I am getting 
> 400 MB writes and 550 MB reads.
I assume the 165ms statistic is actual downtime of the vm during live 
migration, and delays regarding network switching paths are a completely 
external matter. Are you sure the 15-20 seconds you're seeing are actual 
downtime? If you run "while true ; do date ; sleep 1 ; done" on the vm 
while it's migrating, do you see a 15-20 second dropout in the output 
(once it's visible to you)?
I wonder if your IP switches have some sort of arp flap limiting going 
on. You might try disabling spanning tree if that's enabled.
--
Jefferson Ogata : Internetworker, Antibozo

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