IVdsVolumeShrink::Shrink method (vds.h)

[Beginning with Windows 8 and Windows Server 2012, the Virtual Disk Service COM interface is superseded by the Windows Storage Management API.]

Shrinks the volume and all plexes and returns the released extents.

Syntax

HRESULT Shrink(
  [in]  ULONGLONG ullDesiredNumberOfReclaimableBytes,
  [in]  ULONGLONG ullMinNumberOfReclaimableBytes,
  [out] IVdsAsync **ppAsync
);

Parameters

[in] ullDesiredNumberOfReclaimableBytes

Maximum number of bytes by which to shrink the size of the volume. The value of this parameter must be greater than or equal to the value of the ullMinNumberOfReclaimableBytes parameter. If the number of bytes specified is not a multiple of the file system cluster size, the Shrink method will round this value up to the next multiple of the file system cluster size.

[in] ullMinNumberOfReclaimableBytes

Minimum number of bytes by which to shrink the size of the volume. If the volume size cannot be shrunk by at least this number of bytes, the Shrink method fails. If the number of bytes specified is not a multiple of the file system cluster size, the Shrink method will round this value up to the next multiple of the file system cluster size. Specify zero to indicate that no minimum number of reclaimable bytes is required for the Shrink method to succeed.

[out] ppAsync

The address of an IVdsAsync interface pointer. VDS initializes the interface on return. Callers must release the interface. Use this interface to cancel, wait for, or query the status of the operation. If IVdsAsync::Wait is called and a success HRESULT value is returned, the interfaces returned in the VDS_ASYNC_OUTPUT structure must be released by calling the IUnknown::Release method on each interface pointer. However, if Wait returns a failure HRESULT value, or if the pHrResult parameter of Wait receives a failure HRESULT value, the interface pointers in the VDS_ASYNC_OUTPUT structure are NULL and do not need to be released. You can test for success or failure HRESULT values by using the SUCCEEDED and FAILED macros defined in Winerror.h.

Return value

This method can return standard HRESULT values, such as E_INVALIDARG or E_OUTOFMEMORY, and VDS-specific return values. It can also return converted system error codes using the HRESULT_FROM_WIN32 macro. Errors can originate from VDS itself or from the underlying VDS provider that is being used. Possible return values include the following.

Remarks

The Shrink method moves the files so that they are as close as possible to the beginning of the volume, in order to consolidate free space at the end of the volume. (The amount of free space that can be consolidated at the end of the volume determines how much the volume can be shrunk.) It then truncates the file system volume, reducing its size, and then truncates the partition or dynamic volume.

In almost all cases, there will be some files that are immovable (that is, files that cannot be moved). For example, file system and storage driver metadata files are likely to be immovable. For this reason, the amount by which a volume can be shrunk is usually less than the total amount of free space on the volume.

The number and placement of immovable files can vary from one computer to the next, even if both computers are configured identically.

It is possible for a file to be temporarily immovable. For this reason, an application may be able to recover additional space if it calls this method a second time with the same parameters.

If the ullDesiredNumberOfReclaimableBytes and ullMinNumberOfReclaimableBytes parameters are both zero, the Shrink method will shrink the volume by as much as possible.

Shrink and extend operations are supported only on NTFS and RAW volumes.

Use this method to shrink the file system and volume. If VDS fails to shrink the volume, it stops the operation without shrinking the file system.

Only one shrink or defragmentation operation can be performed at a time on each volume.Windows Server 2008 and Windows Vista:  Only one shrink or defragmentation operation can be performed at a time on a computer.

Implementers must return a pointer to the IVdsAsync interface for this method, even if the call does not initiate an asynchronous operation.

This method is identical to the IVdsVolume::Shrink method.

You can use the IVdsVolumeShrink::QueryMaxReclaimableBytes method to estimate the number of bytes to be reclaimed by the shrink operation. However, QueryMaxReclaimableBytes can return more bytes than are actually available.

Requirements

See also

IVdsVolume::Extend

IVdsVolumeShrink