Comment 7 for bug 914484

Reviewed: https://review.openstack.org/10045
Committed: http://github.com/openstack/nova/commit/4d3a50a48011b412bf66b1386292f85cccf1db74
Submitter: Jenkins
Branch: master

commit 4d3a50a48011b412bf66b1386292f85cccf1db74
Author: Daniel P. Berrange <email address hidden>
Date: Fri Jul 20 10:26:19 2012 +0100

    Revert "Attach ISO as separate disk if given proper instruction"

    The following commit

      commit b63a3e8cbd8fe57d0be119368bf47964543270c2
      Author: Josh Kearney <email address hidden>
      Date: Fri Jul 13 15:57:54 2012 -0500

        Attach ISO as separate disk if given proper instruction.

        This gives the option to attach the ISO as a separate drive, like we do in
        XenServer, and boot from that instead of replacing the root drive.

        Fixes bug 914484.

        Change-Id: I0e0560f5fcbc361b60ff1284e7369997dd770fd9

    Results in this XML config

      <devices>
        <disk type="file" device="cdrom">
          <driver type="qcow2" cache="none"/>
          <source file="instance-00000001/disk"/>
          <target bus="virtio" dev="vda"/>
        </disk>
        <disk type="file" device="cdrom">
          <driver type="qcow2" cache="none"/>
          <source file="instance-00000001/disk"/>
          <target bus="ide" dev="vda"/>
        </disk>
       ...
      </devices>

    which is broken in many ways

     - The same backing file is used in read/write mode on 2 disks
       which will cause data corruption on write.
     - The 'virtio' bus type does not allow device="cdrom" disks
     - The 'dev' attribute is given the same value on 2 disks

    To compound the problems, the original commit completely lacks
    any tests which would have caught the brokeness and/or identified
    what was actually intended.

    Change-Id: If1ec286f98fc91f9f411800bbb0adbf2797d2114
    Signed-off-by: Daniel P. Berrange <email address hidden>