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Creating Physical Disk Resources

Applications may need to obtain access to a disk on a shared bus in order to secure data storage or satisfy dependency requirements for a resource. To make a disk usable as a cluster resource, create a Physical Disk resource for it.

New Physical Disk resources should be created only for available cluster-capable disks. That is, disks that are accessible by all cluster nodes and that are not associated with an existing Physical Disk resource.

Note that the Physical Disk resources cannot be created for partitions or logical drives, only entire physical drives. There is currently no way to independently fail over drive partitions on the same disk. A Physical Disk resource can be created for a partitioned drive, but the resource is associated with the entire disk, partitions and all.

Aa369328.wedge(en-us,VS.85).gifTo Create a Physical Disk Resource

  1. Determine search criteria for selecting a disk. Refer to CLUSPROP_PARTITION_INFO and CLUSPROP_PARTITION_INFO_EX for the kinds of data that can be searched for.
  2. Create or select a group in which to create the new resource (see CreateClusterGroup and OpenClusterGroup.)
  3. Get a list of available disks. Call ClusterResourceTypeControl with the CLUSCTL_RESOURCE_TYPE_STORAGE_GET_AVAILABLE_DISKS or CLUSCTL_RESOURCE_TYPE_STORAGE_GET_AVAILABLE_DISKS_EX control code.
  4. Parse the resulting value list for a disk matching the criteria determined in step 1. (See Parsing a Value List.) If a disk is found:
    • Get the signature or GUID of the disk.
    • Get the drive letters of all partitions of the disk.
  5. Create a resource by calling CreateClusterResource, specifying "Physical Disk" as the resource type.
  6. Set the new resource's DiskSignature or DiskIdGuid private property to the signature or GUID obtained in step 4. You must set one or the other of these properties, but not both. Do not change either property after this assignment is made.

Once created, the Physical Disk resource can be brought online, used as a dependency, or otherwise controlled with the Resource Management Functions. It will appear as a cluster resource in failover cluster cmdlet reporting commands.

Windows Server 2008 and Windows Server 2003:  The Physical Disk resource appears as a cluster resource in Cluster.exe.

Windows Server 2003:  The Physical Disk resource appears as a cluster resource in Cluster Administrator.

Example Code

The following example creates a Physical Disk resource for a disk identified by drive letter.


#include "ClusDocEx.h"


// ClusDocEx_ResCreateDisk
// Creates an instance of a Physical Disk resource and returns a 
// handle to it.
// Note:
//   * Do not change the Signature private property of the resource 
//     after it has been created.
//   * To remove the disk from the cluster's control, call 
//     DeleteClusterResource on the returned handle.
// Arguments:
//   IN HCLUSTER hCluster       Cluster handle.
//   IN HGROUP   hGroup         Handle to the group that will contain 
//                              the new resource.
//   IN LPWSTR   lpszDriveLtr   Drive letter of the disk 
//                              for which to create a resource.
// Return Value:
//     Resource handle or NULL for non-success. Call GetLastError() 
//     for more info.
HRESOURCE ClusDocEx_ResCreateDisk
  IN HCLUSTER hCluster,
  IN HGROUP   hGroup,
  IN LPWSTR   lpszDriveLtr
  HRESOURCE hResource = NULL;

  DWORD dwResult        = ERROR_SUCCESS;
  DWORD dwTestSignature = 0;
  DWORD dwSignature     = 0;
  DWORD dwSyntax        = 0;
  DWORD cbLength        = 0;
  DWORD cbRequired      = 0;
  DWORD cbPosition      = 0;

  LPWSTR lpszResName = ( LPWSTR )LocalAlloc( LPTR, MAX_PATH );
  LPWSTR lpszDrives  = L"Drives ";
  LPVOID pValueList  = NULL;

  BOOL bDiskFound = FALSE;


// Begin property list used to set the Signature private property.
// This example uses a struct to define the property list.

  WCHAR szPropName[] = L"Signature"; 

  typedef struct _DiskSignatureControl 
    DWORD dwPropCount;
   } DiskSignatureControl;

  DiskSignatureControl DSC;

  //  Property Count
  DSC.dwPropCount = 1;

  //  Property Name
  DSC.PropName.Syntax.dw  = CLUSPROP_SYNTAX_NAME;
  DSC.PropName.cbLength   = sizeof( szPropName );
  StringCbCopy( DSC.PropName.sz, DSC.PropName.cbLength, szPropName );

  //  Property Value
  DSC.Signature.cbLength  = sizeof( DWORD );
  DSC.Signature.dw        = 0; // this will be changed later
  //  Endmark

  DWORD cbSize = sizeof( DiskSignatureControl );

  //  End property list creation

  if( lpszResName == NULL || 
       pValueList == NULL || 
       lpszDrives == NULL )
    goto endf;

// Get all available disks
// ClusDocEx_RtpGetControlCodeOutput is defined in 
// "Getting Information with Control Codes."

  pValueList = ClusDocEx_RtpGetControlCodeOutput(
                           L"Physical Disk",
                           &cbRequired );

  if( pValueList == NULL )
    goto endf;

// Parse the value list.
// The architecture of this list is described under 
// "Value Lists for Storage Class Resources".
// Two objectives:
// 1) Find the signature of the disk containing the specified drive letter.
// 2) Obtain a list of all drive letters associated with that disk.
// To accomplish both objectives, lpszDrives collects all the drive letters
// for a given disk.  If the specified drive letter is found, the loop
// continues until a new signature signals the start of a new disk. Otherwise
// lpszDrives is reinitialized for each new disk.

  cbh.pb = ( PBYTE )pValueList;

  while( 1 )
    dwSyntax = cbh.pSyntax->dw;

    //  The disk signature structure marks the beginning of a new disk.

      //  Save the signature in case it contains the drive letter we're looking for.

      dwTestSignature = cbh.pDwordValue->dw;

      if( bDiskFound )
        //  The previous disk contained the specified drive letter
        //  lpszDrives lists all drive letters for that disk
      else if( lpszDrives != NULL ) 
        //  Clear the drive letter list for the new disk
        LocalFree( lpszDrives );
        lpszDrives = ( LPWSTR )LocalAlloc( LPTR, MAX_PATH );
        if( lpszDrives == NULL ) goto endf;
        StringCbCopy( lpszDrives, 18, L"Drives: " );


    // Will get one partition info structure per disk partition    

    else if( dwSyntax == CLUSPROP_SYNTAX_PARTITION_INFO )
      // Add the drive letter of this partition to lpszDrives

      StringCchCatW( lpszDrives, MAX_PATH, cbh.pPartitionInfoValue->szDeviceName ); 
      StringCchCatW( lpszDrives, MAX_PATH, L" " ); 

      if( lstrcmpi( cbh.pPartitionInfoValue->szDeviceName, lpszDriveLtr ) == 0 )
        //  The current disk contains the partition with the drive letter
        //  we're looking for.  Flag the find and save the signature.
        bDiskFound = TRUE;
        dwSignature = dwTestSignature;

    else if( dwSyntax == CLUSPROP_SYNTAX_ENDMARK )

    cbLength = cbh.pValue->cbLength;

    // If next advance is within value list buffer, 
    // advance the structure pointer.

    cbPosition += ClusDocEx_ListEntrySize( cbLength );

    if( ( cbPosition + sizeof( DWORD ) ) >= cbRequired ) break;

    cbh.pb += ClusDocEx_ListEntrySize( cbLength );


  if( bDiskFound == FALSE ) goto endf;

// Create the resource.  The resource name is "Disk Drives @: @: @: ... " 
// where @ is the drive letter of a disk partition.

  StringCchCopyW( lpszResName, MAX_PATH, L"Disk " );

  StringCchCatW( lpszResName, MAX_PATH, lpszDrives );

  hResource = CreateClusterResource( hGroup,
                                     L"Physical Disk",
                                     0 );

  if( hResource == NULL )
    dwResult = GetLastError();
    goto endf;

// Update the property list

  DSC.Signature.dw = dwSignature;

// Store the signature in the resource's Signature private property

  dwResult = ClusterResourceControl( hResource,
                                     ( void* ) &DSC,
                                     NULL );

  if( dwResult != ERROR_SUCCESS )
    DeleteClusterResource( hResource );
    CloseClusterResource( hResource );
    hResource = NULL;


  LocalFree( pValueList );
  LocalFree( lpszResName );
  LocalFree( lpszDrives );

  SetLastError( dwResult );

  return hResource;
//  end ClusDocEx_ResCreateDisk



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