[Openstack-operators] Live migration
Diego Parrilla Santamaría
diego.parrilla.santamaria at gmail.com
Thu Sep 6 19:38:03 UTC 2012
I think you are mixing live migration of VMs and compute node fail over.
Live migration assumes your compute nodes are running healthy (or healthy
enough) and you want to move VMs around in order to perform updates or fix
problems on specific nodes.
Failure detection of a compute node seems to be easy, but it's not. There
are a ton of events that could raise a false positive and the logic to
filter these events and perform a recovery could lead to VM duplication:
the same VM running in two compute nodes at the same time. That's the
reason we let our customers to use our APIs to implement their own fail
detection process and then trigger the fail over action.
Compute node failover means one or more compute nodes fail and you need to
replace the failing compute nodes with some spare server you have around
preconfigured in your datacenter. If the problem in the compute node is not
complete, you might live migrate the VMs first, and then replace the
compute node. This is not a complex task with Openstack.
But, if the failure in the compute node is complete, then you need to
replace the compute node and recover the existing configuration of the node
as your previous node. The state of your VMs are lost, but Openstack can
spin them up again. The latter needs not only shared storage, but some
logic to recover the OS configuration, nova-compute configuration, and the
most important thing: libvirt configuration (if you are running KVM, of
*www.stackops.com | * diego.parrilla at stackops.com** | +34 649 94 43 29 |
On Thu, Sep 6, 2012 at 9:16 PM, Paul Walton <paul.d.walton at gmail.com> wrote:
> Well, I guess my real question next is, what happens when a VM is running
> on a compute node and that node simply fails for whatever reason? Does
> OpenStack have any way to detect a compute node failure, and attempt to
> migrate its VMs to another node? I realize that the real VM and the
> migrated VM may be out of sync with each other, but I'm assuming that a
> relatively recent version of the VM is still present on the distributed
> file system to facilitate migration.
> Obviously, regular backups would be required for a real disaster recovery,
> but the VMs I'm talking about won't be changing much, and being a few
> minutes out of sync won't be a problem.
> On Thu, Sep 6, 2012 at 1:32 PM, Joe Topjian <joe.topjian at cybera.ca> wrote:
>> Hi Paul,
>> OpenStack does not have anything like this yet. Anton Beloglazov has
>> created a blueprint from some research work he's done that would provide
>> such a feature:
>> On Thu, Sep 6, 2012 at 12:26 PM, Paul Walton <paul.d.walton at gmail.com>wrote:
>>> I have a quick question about live migration of VMs. I can see how to
>>> do this manually from the command line, i.e. if I want to move a VM from
>>> one compute node to another myself, but I was wondering if there is a way
>>> to have OpenStack do this automatically for me to balance the load across
>>> all the compute nodes dynamically?
>>> Paul Walton
>>> University of Arkansas
>>> College of Engineering
>>> CSCE Technical Support Team
>>> J.B. Hunt Building, Room 440
>>> OpenStack-operators mailing list
>>> OpenStack-operators at lists.openstack.org
>> Joe Topjian
>> Systems Administrator
>> Cybera Inc.
>> Big data is coming to Canada. Join the welcome wagon.
>> *Cyber Summit 2012*
>> October 1-3, Banff
>> Cybera is a not-for-profit organization that works to spur and support
>> innovation, for the economic benefit of Alberta, through the use
>> of cyberinfrastructure.
> Paul Walton
> University of Arkansas
> College of Engineering
> CSCE Technical Support Team
> J.B. Hunt Building, Room 440
> OpenStack-operators mailing list
> OpenStack-operators at lists.openstack.org
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