Thanks for responding.

Others have told me the same--that libvirt is doing its thing in user space. The process of OpenNebula actually clones a copy of the image so this image was freshly created and there's no way it could have been mapped elsewhere.

In other news--by just taking the simple step of putting another
different virtual machine image into ceph and trying again, things actually appear to have worked. more later.

Steve Timm


On Wed, 24 Sep 2014, Robert LeBlanc wrote:

Could this be a lock issue? From what I understand, librbd does not create an 
rbd device, it is all done in
userspace. I would make sure that you have unmapped the image from all machines 
and try it again. I haven't
done a lot with librbd myself, but my co-workers have it working just fine with 
KVM.

On Wed, Sep 24, 2014 at 8:29 AM, Steven Timm <[email protected]> wrote:

      I have been trying for quite some time to launch a KVM VM
      from a CEPH RBD volume using OpenNebula.  I have gotten past the 
permissions issues and to the
      point where kvm can actually
      start a virtual machine, but we are getting a "Geom Error"
      as soon as the virt console comes up.
      (note, not a GRUB Geom error).
      As far as I can tell this means that the kvm bios
      can't understand enough of the geometry of the disk file as presented by 
RBD (which is a RAW
      format image) to even find the boot sector
      to get as far as GRUB.  Have not seen anything with this specific
      error in Google though.

      The hardware that I am using for the Ceph test is going away
      at the end of this week and if I can't get past this problem in
      the next couple days I will have to recommend to my management
      that Ceph is not ready for my production cloud environment.  Appreciate 
the help we have gotten
      thus far and hope the list can come through
      one more time.

      To rehash--I have posted this on other threads before:
      Sci. Linux 6.5 (redhat clone) + Kernel 3.10 + ceph-compiled
      qemu-kvm and qemu-img as downloaded from the Ceph site.

      I can mount the rbd volume outside of qemu/kvm with
      a normal rbd map on the same machine, verify the full
      partition table structure is there and all the files are there.

      KVM must be doing the rbd map and mount correctly because
      I can see the device in question mapped to a /dev/rbd1.

      So I must be dealing with some problem with the format
      of the image, only question is what?   Libvirt is presenting
      the rbd volume to the virtual machine as /dev/vda
      and it was installed on a classic virtual machine (i.e. vda
      was pointing to a partition on a local hard disk) with the boot
      sector on the first sector of vda.

      Any help is appreciated.

      Thanks

      Steve Timm



      ------------------------------------------------------------------
      Steven C. Timm, Ph.D  (630) 840-8525
      [email protected]  http://home.fnal.gov/~timm/
      Fermilab Scientific Computing Division, Scientific Computing Services 
Quad.
      Grid and Cloud Services Dept., Associate Dept. Head for Cloud Computing
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------------------------------------------------------------------
Steven C. Timm, Ph.D  (630) 840-8525
[email protected]  http://home.fnal.gov/~timm/
Fermilab Scientific Computing Division, Scientific Computing Services Quad.
Grid and Cloud Services Dept., Associate Dept. Head for Cloud Computing
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