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[Sebastien Badia <1350857@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

When one live migrates a VM (no shared-storage and qcow2 as the disk image format)
the disk image on the destination compute-node is almost as large as its backing file.

The migration was initiated with : nova live-migration --block-migrate
myvm

On the source compute-node:

compute-0000 ~ # qemu-img info /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
image: /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 6.8M
cluster_size: 65536
backing file: /var/lib/nova/instances/_base/c99ee4f8dc122039d37be31ef5064345acf886be
Format specific information:
    compat: 1.1
    lazy refcounts: false

On the destination compute-node (after successfull migration):

compute-0001 ~ # qemu-img info /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
image: /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
file format: qcow2
virtual size: 20G (21474836480 bytes)
disk size: 18G
cluster_size: 65536
backing file: /var/lib/nova/instances/_base/c99ee4f8dc122039d37be31ef5064345acf886be
Format specific information:
    compat: 1.1
    lazy refcounts: false

** Affects: nova
     Importance: Undecided
         Status: New


** Tags: in-stable-icehouse

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https://bugs.launchpad.net/bugs/1350857

Title:
  Live-migration without shared storage results in a huge qcow2 file

Status in OpenStack Compute (Nova):
  New

Bug description:
  When one live migrates a VM (no shared-storage and qcow2 as the disk image format)
  the disk image on the destination compute-node is almost as large as its backing file.

  The migration was initiated with : nova live-migration --block-migrate
  myvm

  On the source compute-node:

  compute-0000 ~ # qemu-img info /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
  image: /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
  file format: qcow2
  virtual size: 20G (21474836480 bytes)
  disk size: 6.8M
  cluster_size: 65536
  backing file: /var/lib/nova/instances/_base/c99ee4f8dc122039d37be31ef5064345acf886be
  Format specific information:
      compat: 1.1
      lazy refcounts: false

  On the destination compute-node (after successfull migration):

  compute-0001 ~ # qemu-img info /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
  image: /var/lib/nova/instances/1f7865b1-05e7-488d-b339-e11bb7f7fe24/disk
  file format: qcow2
  virtual size: 20G (21474836480 bytes)
  disk size: 18G
  cluster_size: 65536
  backing file: /var/lib/nova/instances/_base/c99ee4f8dc122039d37be31ef5064345acf886be
  Format specific information:
      compat: 1.1
      lazy refcounts: false

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