Retrieves information about the type, size, and nature of a disk partition.

Note  IOCTL_DISK_GET_PARTITION_INFO is superseded by IOCTL_DISK_GET_PARTITION_INFO_EX, which retrieves partition information for AT and Extensible Firmware Interface (EFI) partitions.

To perform this operation, call the DeviceIoControl function with the following parameters.

BOOL DeviceIoControl( (HANDLE) hDevice,                // handle to a partition
                      IOCTL_DISK_GET_PARTITION_INFO,   // dwIoControlCode
                      (LPVOID) NULL,                   // lpInBuffer
                      (DWORD) 0,                       // nInBufferSize
                      (LPVOID) lpOutBuffer,            // output buffer
                      (DWORD) nOutBufferSize,          // size of output buffer
                      (LPDWORD) lpBytesReturned,       // number of bytes returned
                      (LPOVERLAPPED) lpOverlapped );   // OVERLAPPED structure



A handle to the disk device from which partition information is retrieved. To retrieve a device handle, call the CreateFile function.


The control code for the operation. Use IOCTL_DISK_GET_PARTITION_INFO for this operation.


Not used with this operation. Set to NULL.


Not used with this operation. Set to zero.


A pointer to a buffer that receives a PARTITION_INFORMATION data structure.


The size of the output buffer, in bytes. It must be large enough to contain a PARTITION_INFORMATION data structure.


A pointer to a variable that receives the size of the data stored in the output buffer, in bytes.

If the output buffer is too small, the call fails, GetLastError returns ERROR_INSUFFICIENT_BUFFER, and lpBytesReturned is zero.

If lpOverlapped is NULL, lpBytesReturned cannot be NULL. Even when an operation returns no output data and lpOutBuffer is NULL, DeviceIoControl makes use of lpBytesReturned. After such an operation, the value of lpBytesReturned is meaningless.

If lpOverlapped is not NULL, lpBytesReturned can be NULL. If this parameter is not NULL and the operation returns data, lpBytesReturned is meaningless until the overlapped operation has completed. To retrieve the number of bytes returned, call GetOverlappedResult. If hDevice is associated with an I/O completion port, you can retrieve the number of bytes returned by calling GetQueuedCompletionStatus.


A pointer to an OVERLAPPED structure.

If hDevice was opened without specifying FILE_FLAG_OVERLAPPED, lpOverlapped is ignored.

If hDevice was opened with the FILE_FLAG_OVERLAPPED flag, the operation is performed as an overlapped (asynchronous) operation. In this case, lpOverlapped must point to a valid OVERLAPPED structure that contains a handle to an event object. Otherwise, the function fails in unpredictable ways.

For overlapped operations, DeviceIoControl returns immediately, and the event object is signaled when the operation is complete. Otherwise, the function does not return until the operation is complete or an error occurs.

Return value

If the operation completes successfully, DeviceIoControl returns a nonzero value.

If the operation fails or is pending, DeviceIoControl returns zero. To get extended error information, call GetLastError.


The IOCTL_DISK_GET_PARTITION_INFO control code is only supported on MBR-formatted disks.

The disk support can be summarized as follows.

Basic master boot record (MBR)YesYes
Basic GUID partition table (GPT)NoYes
Dynamic MBR boot/systemYesYes
Dynamic MBR dataYesNo
Dynamic GPT boot/systemNoYes
Dynamic GPT dataNoNo


Currently, GPT is supported only on 64-bit systems.

If the partition is on a disk formatted as type master boot record (MBR), partition size totals are limited. For more information, see the Remarks section of IOCTL_DISK_SET_DRIVE_LAYOUT.


Minimum supported client

Windows XP [desktop apps only]

Minimum supported server

Windows Server 2003 [desktop apps only]


WinIoCtl.h (include Windows.h)

See also

Disk Management Control Codes
File System Recognition