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@@ -13,15 +13,15 @@ Parallels Disk Format
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See the COPYING file in the top-level directory.
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This specification contains minimal information about Parallels Disk Format,
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-which is enough to proper work with QEMU. Nevertheless, Parallels Cloud Server
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-and Parallels Desktop are able to add some unspecified nodes to xml and use
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+which is enough to properly work with QEMU. Nevertheless, Parallels Cloud Server
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+and Parallels Desktop are able to add some unspecified nodes to the xml and use
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them, but they are for internal work and don't affect functionality. Also it
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-uses auxiliary xml ``Snapshot.xml``, which allows to store optional snapshot
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-information, but it doesn't influence open/read/write functionality. QEMU and
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-other software should not use fields not covered in this document and
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-``Snapshot.xml`` file and must leave them as is.
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+uses auxiliary xml ``Snapshot.xml``, which allows storage of optional snapshot
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+information, but this doesn't influence open/read/write functionality. QEMU and
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+other software should not use fields not covered in this document or the
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+``Snapshot.xml`` file, and must leave them as is.
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-Parallels disk consists of two parts: the set of snapshots and the disk
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+A Parallels disk consists of two parts: the set of snapshots and the disk
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descriptor file, which stores information about all files and snapshots.
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Definitions
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@@ -29,7 +29,7 @@ Definitions
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Snapshot
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a record of the contents captured at a particular time, capable
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- of storing current state. A snapshot has UUID and parent UUID.
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+ of storing current state. A snapshot has a UUID and a parent UUID.
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Snapshot image
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an overlay representing the difference between this
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@@ -39,13 +39,13 @@ Overlay
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an image storing the different sectors between two captured states.
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Root image
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- snapshot image with no parent, the root of snapshot tree.
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+ a snapshot image with no parent, the root of the snapshot tree.
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Storage
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the backing storage for a subset of the virtual disk. When
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there is more than one storage in a Parallels disk then that
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is referred to as a split image. In this case every storage
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- covers specific address space area of the disk and has its
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+ covers a specific address space area of the disk and has its
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particular root image. Split images are not considered here
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and are not supported. Each storage consists of disk
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parameters and a list of images. The list of images always
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@@ -55,7 +55,7 @@ Storage
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Description file
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``DiskDescriptor.xml`` stores information about disk parameters,
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- snapshots, storages.
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+ snapshots, and storages.
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Top Snapshot
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The overlay between actual state and some previous snapshot.
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@@ -70,9 +70,9 @@ Description file
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All information is placed in a single XML element
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``Parallels_disk_image``.
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-The element has only one attribute ``Version``, that must be ``1.0``.
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+The element has only one attribute, ``Version``, which must be ``1.0``.
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-Schema of ``DiskDescriptor.xml``::
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+The schema of ``DiskDescriptor.xml``::
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<Parallels_disk_image Version="1.0">
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<Disk_Parameters>
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@@ -100,11 +100,11 @@ The ``Disk_Parameters`` element MUST contain the following child elements:
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* ``Heads`` - number of the disk heads.
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* ``Sectors`` - number of the disk sectors per cylinder
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(sector size is 512 bytes)
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- Limitation: Product of the ``Heads``, ``Sectors`` and ``Cylinders``
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+ Limitation: The product of the ``Heads``, ``Sectors`` and ``Cylinders``
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values MUST be equal to the value of the Disk_size parameter.
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* ``Padding`` - must be 0. Parallels Cloud Server and Parallels Desktop may
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- use padding set to 1, however this case is not covered
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- by this spec, QEMU and other software should not open
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+ use padding set to 1; however this case is not covered
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+ by this specification. QEMU and other software should not open
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such disks and should not create them.
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``StorageData`` element
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@@ -121,20 +121,20 @@ as shown below::
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</Storage>
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</StorageData>
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-A ``Storage`` element has following child elements:
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+A ``Storage`` element has the following child elements:
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* ``Start`` - start sector of the storage, in case of non split storage
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equals to 0.
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* ``End`` - number of sector following the last sector, in case of non
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split storage equals to ``Disk_size``.
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* ``Blocksize`` - storage cluster size, number of sectors per one cluster.
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- Cluster size for each "Compressed" (see below) image in
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- parallels disk must be equal to this field. Note: cluster
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- size for Parallels Expandable Image is in ``tracks`` field of
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+ The cluster size for each "Compressed" (see below) image in
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+ a parallels disk must be equal to this field. Note: the cluster
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+ size for a Parallels Expandable Image is in the ``tracks`` field of
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its header (see :doc:`parallels`).
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* Several ``Image`` child elements.
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-Each ``Image`` element has following child elements:
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+Each ``Image`` element has the following child elements:
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* ``GUID`` - image identifier, UUID in curly brackets.
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For instance, ``{12345678-9abc-def1-2345-6789abcdef12}.``
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@@ -145,7 +145,7 @@ Each ``Image`` element has following child elements:
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* ``Plain`` for raw files.
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* ``Compressed`` for expanding disks.
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-* ``File`` - path to image file. Path can be relative to
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+* ``File`` - path to image file. The path can be relative to
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``DiskDescriptor.xml`` or absolute.
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``Snapshots`` element
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@@ -171,17 +171,22 @@ Each ``Shot`` element contains the following child elements:
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* ``GUID`` - an image GUID.
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* ``ParentGUID`` - GUID of the image of the parent snapshot.
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-The software may traverse snapshots from child to parent using ``<ParentGUID>``
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-field as reference. ``ParentGUID`` of root snapshot is
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-``{00000000-0000-0000-0000-000000000000}``. There should be only one root
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-snapshot. Top snapshot could be described via two ways: via ``TopGUID`` child
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-element of the ``Snapshots`` element or via predefined GUID
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+The software may traverse snapshots from child to parent using the
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+``<ParentGUID>`` field as reference. The ``ParentGUID`` of the root
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+snapshot is ``{00000000-0000-0000-0000-000000000000}``.
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+There should be only one root snapshot.
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+
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+The Top snapshot could be
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+described via two ways: via the ``TopGUID`` child
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+element of the ``Snapshots`` element, or via the predefined GUID
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``{5fbaabe3-6958-40ff-92a7-860e329aab41}``. If ``TopGUID`` is defined,
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-predefined GUID is interpreted as usual GUID. All snapshot images
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-(except Top Snapshot) should be
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-opened read-only. There is another predefined GUID,
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+the predefined GUID is interpreted as a normal GUID. All snapshot images
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+(except the Top Snapshot) should be
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+opened read-only.
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+
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+There is another predefined GUID,
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``BackupID = {704718e1-2314-44c8-9087-d78ed36b0f4e}``, which is used by
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-original and some third-party software for backup, QEMU and other
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-software may operate with images with ``GUID = BackupID`` as usual,
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-however, it is not recommended to use this
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-GUID for new disks. Top snapshot cannot have this GUID.
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+original and some third-party software for backup. QEMU and other
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+software may operate with images with ``GUID = BackupID`` as usual.
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+However, it is not recommended to use this
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+GUID for new disks. The Top snapshot cannot have this GUID.
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