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



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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