[libvirt] KVM migration with uri = NULL

Daniel P. Berrange berrange at redhat.com
Mon Apr 20 09:09:38 UTC 2009

On Sun, Apr 19, 2009 at 09:16:53AM +0200, Chris Lalancette wrote:
> Zvi Dubitzky wrote:
> > What is the meaning of using virDomainMigrate () with NULL uri.
> > Looking at the code of  qemudDomainMigratePrepare2 ()/ qemu_driver.c,   I 
> > understand that it tries to perform a migration  to another 
> > VM on the same node  . Is that correct ?
> No, that's not right.  The URI parameter is generally not needed when you are
> doing a live migrate; it's basically there to specify an "alternate" way to
> reach the remote qemu process, but I've haven't come across a case where it is
> useful yet.  That is, you *should* set URI to NULL, and let libvirt handle the
> details.

The time it is useful is if your machine has multiple NICs, you are using
one set of interfaces for management, and want migration to go over a 
different interface that's perhaps more suited for low-latency/high-bandwidth
needs of migration. In this case you'd give a URI refering to the alternate
interface's IP address

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