[CentOS-virt] Basic shared storage + KVM

Tue Jun 19 19:48:00 UTC 2012
Ed Heron <Ed at Heron-ent.com>

On Tue, 2012-06-19 at 18:21 +0200, Andrea Chierici wrote:
> Hi,
> I am trying to set up a shared iscsi storage to serve 6 kvm hypervisors 
> running centos 6.2.
> I export an LVM from iscsi and configured virt-manager to see the iscsi 
> space as LVM storage (a single storage pool).
> I can create space on this LVM storage pool directly from virt-manager 
> and I am already running a couple of sample VMs, that do migrate from 
> one hv to the other.
> This configuration has a problem: when I create a new LV on the LVM 
> storage pool to host a new VM, the HV where I am creating the virtual 
> machine on sees the LV as status "available", while the others see it as 
> "NOT available". In some circumstances this can crash libvirtd. To fix 
> this I generally issue:
> vgchange -an; sleep 1; vgchange -ay
> but sometimes this fails with error:
> device-mapper; create ioctl failed: Device or resource busy
> and anyway it's not very convenient to issue this command on every node 
> every time a new LV is created.
> Can anyone suggest a solution (if any) to this problem?
> Keep in mind that the basic concept behind this approach is to keep 
> things as simple as possible. I don't want to configure a cluster or any 
> other complicated tool to simply be able to migrate VMs from one HV to 
> another.
> Thanks,
> Andrea

  Please help me understand why you are doing it this way?  I'm using
Xen with integrated storage, but I've been considering separating my
storage from my virtual hosts.  Conceptually, we can ignore the Xen/KVM
difference for this discussion.  I would imagine using LVM on the
storage server then setting the LVs up as iSCSI targets.  On the virtual
host, I imagine I would just configure the new device and hand it to my