XEN: Howto migrate loopback file based disk images to blktap tap:aio

  • 7000716
  • 20-Jun-2008
  • 27-Apr-2012

Environment

Novell SUSE Linux Enterprise Server 10 Service Pack 2

Situation

Migrate a loopback file based disk image to a blktap tap:aio disk image without reinstalling the DomU.

Resolution

  1. Backup current DomU configuration:
    xm list <DomU_ID> -l > /tmp/vm1.conf
  2. Edit disk device section of the configuration file:
    vi /tmp/vm1.conf

    # Configuration example

    (device
    (vbd
    (unamefile:/xen/vm1/disk0)
    (uuid d2cb4a14-ecbd-6034-3d4c-7866bfd4b60e)
    (mode w)
    (devxvda:disk)
    (backend 0)
    (bootable 1)
    )
    )

    # Change to

    (device
    (tap
    (uname tap:aio:/xen/vm1/disk0)
    (uuid d2cb4a14-ecbd-6034-3d4c-7866bfd4b60e)
    (mode w)
    (dev xvda:disk)
    (backend 0)
    (bootable 1)
    )
    )

  3. Delete old DomU
    xm delete <DomU_ID>
  4. Load new configuration
    xm new -F /tmp/vm1.conf
  5. Start new DomU
    xm start <DomU_ID>

Additional Information

The advantage of the blktap is a better performance compared to disk images accessed through loopback.  The blktap driver is supported as of SLES10 SP2, however for NetWare this should only be used on NW65SP8.

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