[virt-tools-list] virsh migrate --live has sever bandwidth limits?

[Wen Congyang]

At 10/18/2011 07:18 AM, Phil Meyer Write:
> 
> We are experimenting with large VMs, 4GB, live migrating from one host
> to another.
> 
> At first they were hitting our process timer, so I shut that off.
> 
> We have watched one today that started pushing 40Mb (bits) per second
> from host 1 to host 9 -- both hosts are Dell M610 blades in the same
> chassis with Gbit ports.
> 
> It is still running the migrate after 2.5 hours.  I will be leaving it
> to run over night to see what happens.

If you do live migration, sometimes it takes long time or may not end.
I think your guest is too busy, and the guest's memory is changed continuously.

> 
> We use an intermediate host to talk to each server to initiate the live
> migrate.  ssh keys are set, and this command has always worked on
> smaller, or not busy hosts.
> 
> The KVM in question is running win2k8r2 with 2 virtual CPUs and 4GB RAM.
> The host has 32GB RAM and is not very loaded at the moment.
> 
> Here is the command being executed on the intermediate host:
> 
> [root at pxe1 ~]# virsh -c qemu+ssh://root@kvm1.mydomain.net/system migrate
> --live a008881 qemu+ssh://root@kvm9.mydomain.net/system
> 
> Versions:
> 
> RHEL 6.0
> 
> libvirt-client-0.8.7-14.el6.x86_64
> libvirt-debuginfo-0.8.7-14.el6.x86_64
> virt-viewer-0.2.1-2.el6.x86_64
> libvirt-python-0.8.7-14.el6.x86_64
> libvirt-devel-0.8.7-14.el6.x86_64
> python-virtinst-0.500.3-7.el6.noarch
> libvirt-0.8.7-14.el6.x86_64
> 
> Is there a default 'migrate-setspeed' in the older version, and if so,
> was it ~40Kb ?

The default speed is set in qemu, not libvirt.

You can run migrate-setmaxdowntime to change the downtime to a bigger value,
and I think the migration will end soon.

Thanks
Wen Congyang

> 
> Can it be modified in this version?  There are way too many systems
> involved to do large updates at the moment.  However, a small code
> change to a couple python scripts might slide through. :)
> 
> We will be moving them to RHEL 6.1 or 6.2 in the spring.
> 
> Thanks for any pointers!
> 
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