[CentOS-virt] Live migration and DRBD

Kris Buytaert mlkb at inuits.be
Tue Dec 1 11:53:02 UTC 2009

On Mon, 2009-11-30 at 11:43 -0500, Tait Clarridge wrote:
> On Mon, 2009-11-30 at 13:53 -0200, Gilberto Nunes wrote:
> > Hi folks
> > 
> > I deploy a two Dell PowerEdge T300 to test Virtualization with
> > kvm+drbd+heartbaet.
> > 
> > The KVM drbd and heartbeat work properly.
> > 
> > However, I have doubt!!
> > 
> > When the primary node has down, the secondary node start the VM that
> > has original running on primary node...
> > So, this required a full stop of hole system...
> > This is not we wish here...
> > 
> > Is there something way to live migrate VM from primary node that was
> > shutdown????
> > 
> > I have no idea how to make this stuff working...
> > 
> > Thanks for any help
> > 
> Currently there is work being done on a project for Xen called Remus. I
> am not sure about KVM but Remus is still in development and although it
> has been merged into the xen-unstable repository, it isn't completely
> ready yet (although the developers are working very hard).
> Basically it performs the first part of a live migration and if
> connection is lost, it will jump the virtual machine over to the
> secondary host.
> http://nss.cs.ubc.ca/remus/
> It appears that Red Hat is including "high availability" for KVM in
> their Red Hat Enterprise Virtualization Manager for Servers.
> Not sure if this is going to make it to CentOS, can someone
> confirm/deny?

There are 3 different things being discussed in this thread so far :

 1. Live Migration 
 2. Virtual Machine HA 
 3. Continuous Mirroring / Replication 

(1) First of all Live Migration  is not a HA solution,  if your primary
machine dies , there is no way to initiate a Live Migration anymore, as
Live  migration requires the home node to be still active,  it can be
used to migrate workloads away during maintenance slots etc , or to
spread load, but not for HA.

(2) So what people typically configure with HeartBeat is indeed the
restart of a virtual machine from the same "shared" storage device. 

(3) Remus and Kemari are new kids in town they are going for RealTime
Mirroring and therefore will implement real Virtual Machine HA.
Remus is headed for Xen inclusion, while Kemari has just announced that
they are also starting to work on a KVM port , but their current version
was only Xen targeted.


Hope that clarifies some stuff ..

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