[MS-VDS]: Virtual Disk Service (VDS) Protocol Specification

allocated as the backing store for the virtual disk and that this file will automatically increasein size to accommodate the allocated data.A virtual disk created using the CREATE_ VIRTUAL_DISK_FLAG_NONE flag has a virtual diskfile backing store that at any given time is as large as the actual data written to it, plus thesize of the header and footer. As more data is written, the virtual disk file automaticallyincreases in size.For example, if the CREATE_VIRTUAL_DISK_FLAG_NONE flag is used to create a virtual diskthat is 2 gigabytes in size, the initial size of the virtual disk file backing store may only be 2megabytes. As data is written to this disk, the virtual disk file backing store increases in size,with a maximum size of 2 gigabytes.CREATE_VIRTUAL_DISK_FLAG_FULL_PHYSICAL_ALLOCATION: Specifies that the servershould preallocate all physical space necessary for the virtual size of the virtual disk. A fixedsize virtual disk file will be allocated as the backing store for the virtual disk. For example,creating a fixed size virtual disk that is 2 gigabytes in size using this flag will result in a virtualdisk file that is approximately 2 gigabytes in size.2.2.2.17.2 Structures2.2.2.17.2.1 VDS_CREATE_VDISK_PARAMETERSThe VDS_CREATE_VDISK_PARAMETERS structure contains the parameters to be used when avirtual disk is created.typedef struct _VDS_CREATE_VDISK_PARAMETERS {GUID UniqueId;ULONGLONG MaximumSize;ULONG BlockSizeInBytes;ULONG SectorSizeInBytes;[string] LPWSTR pParentPath;[string] LPWSTR pSourcePath;} VDS_CREATE_VDISK_PARAMETERS,*PVDS_CREATE_VDISK_PARAMETERS;UniqueId: A unique and non-zero GUID value to be assigned to the virtual disk.MaximumSize: The maximum virtual size, in bytes, of the virtual disk object.BlockSizeInBytes: The internal block size, in bytes, of the virtual disk object. If the virtual diskobject being created is a differencing disk, this value MUST be 0. If the virtual disk objectbeing created is not a differencing disk, setting this value to 0 causes the virtual disk objectbeing created to use the default block size.SectorSizeInBytes: Internal sector size, in bytes, of the virtual disk object. This value MUST beset to 512 (CREATE_VIRTUAL_DISK_PARAMETERS_DEFAULT_SECTOR_SIZE).pParentPath: A null-terminated wide-character string containing an optional path to a parentvirtual disk object. This member associates the new virtual hard disk with an existing virtualhard disk. Used when creating a differencing disk. The differencing disk gets its size from itsparent.A differencing disk represents the current state of the virtual disk as a set of modified blocksin comparison to a parent disk. A differencing disk is not independent; it depends on the[MS-VDS] — v20110610Virtual Disk Service (VDS) Protocol SpecificationCopyright © 2011 Microsoft Corporation.Release: Friday, June 10, 201184 / 360