Question

When I list virtual disks within diskpart:

DISKPART> list vdisk

  VDisk ###  Disk ###  State                 Type       File
  ---------  --------  --------------------  ---------  ----
  VDisk 0    Disk 2    Attached not open     Fixed       C:\Disk.vhd

Interesting part for me here is file name. I tried to find equivalent of function that would give me file name (under File column) if I know disk number.

Ideally, I would give “\\?\PhysicalDrive2” and I would get “C:\Disk.vhd” as result.

I already tried:

1. Using diskpart and parsing output – since it is undocumented format, it can change at any time. This is not something I would rely on.
2. General VHD API – no function takes disk number as parameter.
3. Microsoft.Storage.Vds.dll – There are enumerations that go through each drive (e.g. Service.Providers) but there is no property/function that will give me name of source file. While I can now be sure that e.g. drive D: is virtual drive, I still cannot know which .vhd file was attached.

Any idea which function that might be?

Answer 1

Here are two solutions to retrieve virtual disks on the local machine and to print their information. The two solutions demonstrate how to use VDS COM objects to access these data both in a native and managed way.

Managed Solution

I have create a partial COM Interop from the MSDN Documentation and from the Windows 7 SDK (mainly vds.h). Note that the COM wrappers are partial, which means that some methods are yet to be ported.

Below is a managed application that uses the .NET COM interop to:

• Load the VDS service
• Query for the Virtual Disk Providers
• List all the Virtual Disk handled by each provider:
  • The virtual disk’s properties gives its GUID, its full driver path, its volume size and its disk file (i.e. C:\Disk.vhd).
  • A virtual disk can be also be queried as a generic disk and gives its name (i.e. \\?\PhysicalDrive1), its friendly name and other properties.

---

using System;
using System.Runtime.InteropServices;

namespace VDiskDumper
{
    class Program
    {
        static void Main(string[] args)
        {
            // Create the service loader
            VdsServiceLoader loaderClass = new VdsServiceLoader();
            IVdsServiceLoader loader = (IVdsServiceLoader)loaderClass;
            Console.WriteLine("Got Loader");

            // Load the service
            IVdsService service;
            loader.LoadService(null, out service);
            Console.WriteLine("Got Service");

            // Wait for readyness
            service.WaitForServiceReady();
            Console.WriteLine("Service is ready");

            // Query for vdisk providers
            IEnumVdsObject providerEnum;
            service.QueryProviders(VDS_QUERY_PROVIDER_FLAG.VDS_QUERY_VIRTUALDISK_PROVIDERS, out providerEnum);
            Console.WriteLine("Got Providers");

            // Iterate
            while (true)
            {
                uint fetched;
                object unknown;
                providerEnum.Next(1, out unknown, out fetched);

                if (fetched == 0) break;

                // Cast to the required type
                IVdsVdProvider provider = (IVdsVdProvider)unknown;
                Console.WriteLine("Got VD Provider");

                Dump(provider);
            }

            Console.ReadKey();
        }

        private static void Dump(IVdsVdProvider provider)
        {
            // Query for the vdisks
            IEnumVdsObject diskEnum;
            provider.QueryVDisks(out diskEnum);
            Console.WriteLine("Got VDisks");

            // Iterate
            while (true)
            {
                uint fetched;
                object unknown;
                diskEnum.Next(1, out unknown, out fetched);

                if (fetched == 0) break;

                // Cast to the required type
                IVdsVDisk vDisk = (IVdsVDisk)unknown;

                // Get the vdisk properties
                VDS_VDISK_PROPERTIES vdiskProperties;
                vDisk.GetProperties(out vdiskProperties);

                Console.WriteLine("-> VDisk Id=" + vdiskProperties.Id);
                Console.WriteLine("-> VDisk Device Name=" + vdiskProperties.pDeviceName);
                Console.WriteLine("-> VDisk Path=" + vdiskProperties.pPath);

                // Get the associated disk
                IVdsDisk disk;
                provider.GetDiskFromVDisk(vDisk, out disk);

                // Get the disk properties
                VDS_DISK_PROP diskProperties;
                disk.GetProperties(out diskProperties);

                Console.WriteLine("-> Disk Name=" + diskProperties.pwszName);
                Console.WriteLine("-> Disk Friendly=" + diskProperties.pwszFriendlyName);
            }
        }
    }

    [ComImport, Guid("118610b7-8d94-4030-b5b8-500889788e4e"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IEnumVdsObject
    {
        void Next(uint numberOfObjects, [MarshalAs(UnmanagedType.IUnknown)] out object objectUnk, out uint numberFetched);
        void Skip(uint NumberOfObjects);
        void Reset();
        void Clone(out IEnumVdsObject Enum);
    }

    [ComImport, Guid("07e5c822-f00c-47a1-8fce-b244da56fd06"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IVdsDisk
    {
        void GetProperties(out VDS_DISK_PROP diskProperties);
        void GetPack(); // Unported method
        void GetIdentificationData(IntPtr lunInfo);
        void QueryExtents(); // Unported method
        void slot4();
        void SetFlags(); // Unported method
        void ClearFlags(); // Unported method
    }

    [ComImport, Guid("0818a8ef-9ba9-40d8-a6f9-e22833cc771e"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IVdsService
    {
        [PreserveSig]
        int IsServiceReady();
        [PreserveSig]
        int WaitForServiceReady();
        void GetProperties(); // Unported method
        void QueryProviders(VDS_QUERY_PROVIDER_FLAG mask, out IEnumVdsObject providers);
        void QueryMaskedDisks(out IEnumVdsObject disks);
        void QueryUnallocatedDisks(out IEnumVdsObject disks);
        void GetObject(); // Unported method
        void QueryDriveLetters(); // Unported method
        void QueryFileSystemTypes(out IntPtr fileSystemTypeProps, out uint numberOfFileSystems);
        void Reenumerate();
        void Refresh();
        void CleanupObsoleteMountPoints();
        void Advise(); // Unported method
        void Unadvise(); // Unported method
        void Reboot();
        void SetFlags(); // Unported method
        void ClearFlags(); // Unported method
    }

    [ComImport, Guid("e0393303-90d4-4a97-ab71-e9b671ee2729"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IVdsServiceLoader
    {
        void LoadService([In, MarshalAs(UnmanagedType.LPWStr)] string machineName, out IVdsService vdsService);
    }

    [ComImport, Guid("1e062b84-e5e6-4b4b-8a25-67b81e8f13e8"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IVdsVDisk
    {
        void Open(); // Unported method
        void GetProperties(out VDS_VDISK_PROPERTIES pDiskProperties);
        void GetHostVolume(); // Unported method
        void GetDeviceName(); // Unported method
    }

    [ComImport, Guid("b481498c-8354-45f9-84a0-0bdd2832a91f"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IVdsVdProvider
    {
        void QueryVDisks(out IEnumVdsObject ppEnum);
        void CreateVDisk(); // Unported method
        void AddVDisk(); // Unported method
        void GetDiskFromVDisk(IVdsVDisk pVDisk, out IVdsDisk ppDisk);
        void GetVDiskFromDisk(IVdsDisk pDisk, out IVdsVDisk ppVDisk);
    }

    [ComImport, Guid("9c38ed61-d565-4728-aeee-c80952f0ecde")]
    public class VdsServiceLoader
    {
    }

    [StructLayout(LayoutKind.Explicit)]
    public struct Signature
    {
        [FieldOffset(0)]
        public uint dwSignature;
        [FieldOffset(0)]
        public Guid DiskGuid;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct VDS_DISK_PROP
    {
        public Guid Id;
        public VDS_DISK_STATUS Status;
        public VDS_LUN_RESERVE_MODE ReserveMode;
        public VDS_HEALTH health;
        public uint dwDeviceType;
        public uint dwMediaType;
        public ulong ullSize;
        public uint ulBytesPerSector;
        public uint ulSectorsPerTrack;
        public uint ulTracksPerCylinder;
        public uint ulFlags;
        public VDS_STORAGE_BUS_TYPE BusType;
        public VDS_PARTITION_STYLE PartitionStyle;
        public Signature dwSignature;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pwszDiskAddress;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pwszName;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pwszFriendlyName;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pwszAdaptorName;
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pwszDevicePath;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct VIRTUAL_STORAGE_TYPE
    {
        public uint DeviceId;
        public Guid VendorId;
    }

    [StructLayout(LayoutKind.Sequential)]
    public struct VDS_VDISK_PROPERTIES
    {
        public Guid Id;
        public VDS_VDISK_STATE State;
        public VIRTUAL_STORAGE_TYPE VirtualDeviceType;
        public ulong VirtualSize;
        public ulong PhysicalSize;
        [MarshalAs(UnmanagedType.LPWStr)]
        public String pPath;
        [MarshalAs(UnmanagedType.LPWStr)]
        public String pDeviceName;
        public DEPENDENT_DISK_FLAG DiskFlag;
        public bool bIsChild;
        [MarshalAs(UnmanagedType.LPWStr)]
        public String pParentPath;
    }

    public enum DEPENDENT_DISK_FLAG
    {
        DEPENDENT_DISK_FLAG_NONE = 0x00000000,
        DEPENDENT_DISK_FLAG_MULT_BACKING_FILES = 0x00000001,
        DEPENDENT_DISK_FLAG_FULLY_ALLOCATED = 0x00000002,
        DEPENDENT_DISK_FLAG_READ_ONLY = 0x00000004,
        DEPENDENT_DISK_FLAG_REMOTE = 0x00000008,
        DEPENDENT_DISK_FLAG_SYSTEM_VOLUME = 0x00000010,
        DEPENDENT_DISK_FLAG_SYSTEM_VOLUME_PARENT = 0x00000020,
        DEPENDENT_DISK_FLAG_REMOVABLE = 0x00000040,
        DEPENDENT_DISK_FLAG_NO_DRIVE_LETTER = 0x00000080,
        DEPENDENT_DISK_FLAG_PARENT = 0x00000100,
        DEPENDENT_DISK_FLAG_NO_HOST_DISK = 0x00000200,
        DEPENDENT_DISK_FLAG_PERMANENT_LIFETIME = 0x00000400,
    }

    public enum VDS_DISK_STATUS
    {
        VDS_DS_UNKNOWN = 0,
        VDS_DS_ONLINE = 1,
        VDS_DS_NOT_READY = 2,
        VDS_DS_NO_MEDIA = 3,
        VDS_DS_FAILED = 5,
        VDS_DS_MISSING = 6,
        VDS_DS_OFFLINE = 4
    }

    public enum VDS_HEALTH
    {
        VDS_H_UNKNOWN = 0,
        VDS_H_HEALTHY = 1,
        VDS_H_REBUILDING = 2,
        VDS_H_STALE = 3,
        VDS_H_FAILING = 4,
        VDS_H_FAILING_REDUNDANCY = 5,
        VDS_H_FAILED_REDUNDANCY = 6,
        VDS_H_FAILED_REDUNDANCY_FAILING = 7,
        VDS_H_FAILED = 8,
        VDS_H_REPLACED = 9,
        VDS_H_PENDING_FAILURE = 10,
        VDS_H_DEGRADED = 11
    }

    public enum VDS_LUN_RESERVE_MODE
    {
        VDS_LRM_NONE = 0,
        VDS_LRM_EXCLUSIVE_RW = 1,
        VDS_LRM_EXCLUSIVE_RO = 2,
        VDS_LRM_SHARED_RO = 3,
        VDS_LRM_SHARED_RW = 4
    }

    public enum VDS_PARTITION_STYLE
    {
        VDS_PST_UNKNOWN = 0,
        VDS_PST_MBR = 1,
        VDS_PST_GPT = 2
    }

    public enum VDS_QUERY_PROVIDER_FLAG
    {
        VDS_QUERY_SOFTWARE_PROVIDERS = 0x1,
        VDS_QUERY_HARDWARE_PROVIDERS = 0x2,
        VDS_QUERY_VIRTUALDISK_PROVIDERS = 0x4
    }

    public enum VDS_STORAGE_BUS_TYPE
    {
        VDSBusTypeUnknown = 0,
        VDSBusTypeScsi = 0x1,
        VDSBusTypeAtapi = 0x2,
        VDSBusTypeAta = 0x3,
        VDSBusType1394 = 0x4,
        VDSBusTypeSsa = 0x5,
        VDSBusTypeFibre = 0x6,
        VDSBusTypeUsb = 0x7,
        VDSBusTypeRAID = 0x8,
        VDSBusTypeiScsi = 0x9,
        VDSBusTypeSas = 0xa,
        VDSBusTypeSata = 0xb,
        VDSBusTypeSd = 0xc,
        VDSBusTypeMmc = 0xd,
        VDSBusTypeMax = 0xe,
        VDSBusTypeFileBackedVirtual = 0xf,
        VDSBusTypeMaxReserved = 0x7f
    }

    public enum VDS_VDISK_STATE
    {
        VDS_VST_UNKNOWN = 0,
        VDS_VST_ADDED,
        VDS_VST_OPEN,
        VDS_VST_ATTACH_PENDING,
        VDS_VST_ATTACHED_NOT_OPEN,
        VDS_VST_ATTACHED,
        VDS_VST_DETACH_PENDING,
        VDS_VST_COMPACTING,
        VDS_VST_MERGING,
        VDS_VST_EXPANDING,
        VDS_VST_DELETED,
        VDS_VST_MAX
    }
}

---

Native Solution

Below is a native application that uses the VDS COM interfaces to:

• Load the VDS service
• Query for the Virtual Disk Providers
• List all the Virtual Disk handled by each provider:
  • The virtual disk’s properties gives its GUID, its full driver path, its volume size and its disk file (i.e. C:\Disk.vhd).
  • A virtual disk can be also be queried as a generic disk and gives its name (i.e. \\?\PhysicalDrive1), its friendly name and other properties.

---

#include "initguid.h"
#include "vds.h"
#include <stdio.h>

#pragma comment( lib, "ole32.lib" )
#pragma comment( lib, "rpcrt4.lib" )

// Simple macro to release non-null interfaces.
#define _SafeRelease(x) {if (NULL != x) { x->Release(); x = NULL; } }

void exploreVDiskProvider(IVdsVdProvider *pVdProvider);

int __cdecl main(void) 
{
    HRESULT hResult;
    ULONG ulFetched = 0;
    BOOL bDone = FALSE;

    IVdsServiceLoader *pLoader = NULL;
    IVdsService *pService = NULL;
    IEnumVdsObject *pProviderEnum = NULL;
    IUnknown *pUnknown = NULL;
    IVdsVdProvider *pVdProvider = NULL;

    // Initialize COM
    hResult = CoInitialize(NULL);
    if (FAILED(hResult)) goto bail;

    // For this, get a pointer to the VDS Loader
    hResult = CoCreateInstance(CLSID_VdsLoader,
        NULL,
        CLSCTX_LOCAL_SERVER,
        IID_IVdsServiceLoader,
        (void **) &pLoader);
    if (FAILED(hResult)) goto bail;

    printf("Loading VDS Service...\n");

    // Launch the VDS service. 
    hResult = pLoader->LoadService(NULL, &pService);

    // We're done with the Loader interface at this point.
    _SafeRelease(pLoader); 

    if (FAILED(hResult)) goto bail;

    // Wait for service to be ready
    hResult = pService->WaitForServiceReady();
    if (FAILED(hResult)) goto bail;

    printf("VDS Service Loaded\n");

    // Query for virtual disk providers
    hResult = pService->QueryProviders(VDS_QUERY_VIRTUALDISK_PROVIDERS, &pProviderEnum);
    if (FAILED(hResult)) goto bail;

    printf("Querying providers...\n");

    // Iterate over virtual disk providers
    while(1) 
    {
        ulFetched = 0;
        hResult = pProviderEnum->Next(1, &pUnknown, &ulFetched);
        if (FAILED(hResult)) {
            break;
        }
        if (hResult == S_FALSE) {
            break;
        }

        // Cast the current value to a virtual disk provider
        hResult = pUnknown->QueryInterface(IID_IVdsVdProvider, (void **) &pVdProvider); 
        if (FAILED(hResult)) goto bail;

        printf("VDS Virtual Disk Provider Found\n");

        exploreVDiskProvider(pVdProvider);

        _SafeRelease(pVdProvider);

        _SafeRelease(pUnknown);
    }

    getchar();
    return 0;

bail:
    printf("Failed hr=%x\n", hResult);
    return 1;
}

void exploreVDiskProvider(IVdsVdProvider *pVdProvider) {
    HRESULT hResult;
    ULONG ulFetched = 0;

    IEnumVdsObject *pVDiskEnum = NULL;
    IVdsVDisk *pVDisk = NULL;
    IUnknown *pUnknown = NULL;
    IVdsVolume *pVolume = NULL;
    VDS_VDISK_PROPERTIES vdiskProperties = { 0 };
    TCHAR *uuid = NULL;
    IVdsDisk *pDisk = NULL;
    VDS_DISK_PROP diskProperties = { 0 };

    // Query the disks handled by the provider
    hResult = pVdProvider->QueryVDisks(&pVDiskEnum);
    if (FAILED(hResult)) goto bail;

    printf("Querying virtual disks...\n");

    // Iterate over virtual disks
    while(1) 
    {
        ulFetched = 0;
        hResult = pVDiskEnum->Next(1, &pUnknown, &ulFetched);
        if (hResult == S_FALSE) {
            break;
        }

        if (FAILED(hResult)) goto bail;

        // Cast the current value to a disk
        hResult = pUnknown->QueryInterface(IID_IVdsVDisk, (void **) &pVDisk);
        if (FAILED(hResult)) goto bail;

        printf("Virtual disk Found\n");

        // Get the disk's properties and display some of them
        hResult = pVDisk->GetProperties(&vdiskProperties);
        if (FAILED(hResult)) goto bail;

        // Convert the GUID to a string
        UuidToString(&vdiskProperties.Id, (RPC_WSTR *) &uuid);

        // Dump some properties
        printf("-> Disk Id=%ws\n", uuid);
        printf("-> Disk Device Name=%ws\n", vdiskProperties.pDeviceName);
        printf("-> Disk Path=%ws\n", vdiskProperties.pPath);

        // Get the disk instance from the virtual disk
        hResult = pVdProvider->GetDiskFromVDisk(pVDisk, &pDisk);
        if (FAILED(hResult)) goto bail;

        _SafeRelease(pVDisk);

        _SafeRelease(pUnknown);

        // Get the disk's properties and display some of them
        hResult = pDisk->GetProperties(&diskProperties);
        if (FAILED(hResult)) goto bail;

        printf("-> Disk Name=%ws\n", diskProperties.pwszName);
        printf("-> Disk Friendly Name=%ws\n", diskProperties.pwszFriendlyName);
    }

    return;

bail:
    printf("Failed hr=%x\n", hResult);
}