A description of the new Disk Unique ID feature of Windows Clustering in Windows Server 2003 Service Pack 1 and in x64-based versions of Windows Server 2003 (883286)

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Clusdisk Disk Unique ID overview

By default, in Windows Server 2003 SP1 and in x64-based versions of Windows Server 2003, the Clusdisk component uses the new Disk Unique ID feature instead of disk signatures to identify disks. Clusdisk still uses disk signatures to identify legacy disks and for backward compatibility with the original release version of Windows Server 2003 and Microsoft Windows 2000 Server server clusters. The new Clusdisk component still recognizes and handles changes to disk signatures. However, by using the Disk Unique ID feature, Clusdisk reduces the number of device reset operations that Clusdisk sends. This new Clusdisk feature is compatible with legacy hard disks. Therefore, this new feature is compatible with hard disks that do not support the Disk Unique ID feature.

Because of this new Disk Unique ID feature, a new DiskUniqueIds property appears in the cluster disk resource private properties. To view this property, type the following command at a command prompt, and then press ENTER, where letter is the drive letter of the disk that you want to view the properties of:

cluster res "disk letter:" /priv

For example, to view the properties of the disk that the letter II is assigned to, type the following command, and then press ENTER:

cluster res "disk i:" /priv

Information that is similar to the following is returned:

Listing private properties for 'disk i:':

T  Resource             Name                           Value
-- -------------------- ------------------------------ -----------------------
D  disk i:              Signature                      2545596169 (0x97bab709)
D  disk i:              SkipChkdsk                     0 (0x0)
D  disk i:              ConditionalMount               1 (0x1)
M  disk i:              MPVolGuids                     7e00 \??\Volume{0b3afeff-9881-11d7-9ac5-505054503030}
S  disk i:              SerialNumber                   ZG02206609
B  disk i:              DiskUniqueIds                  10 00 00 00 ... (48 bytes)
B  disk i:              MountVolumeInfo                09 B7 BA 97 ... (32 bytes)

Clusdisk Unique Disk ID functionality

The new Clusdisk Unique Disk ID feature is intended to reduce the chance that a disk is unavailable in the server cluster. Therefore, the number of device resets that Clusdisk sends is one. This device reset is sent only when the last disk owner has become unavailable but has not released the disk reserve. Clusdisk does not send a device reset under any other circumstances. Additionally, the default number of arbitration attempts for a disk has been changed from five in the original release version to two in SP1.

Clusdisk behaviors for disks that support unique identifiers

Clusdisk now has the following behaviors for disks that support unique identifiers (IDs):

The disk resource stores and propagates a disk's unique identifiers in the following registry subkey:
HKEY_LOCAL_MACHINE\Cluster\Resources\GUID\Parameters\DiskUniqueIds
When a disk comes online, or during the arbitration of the disk resource, Clusdisk uses the disk's unique IDs to locate that disk.
After Clusdisk successfully identifies the disk, Clusdisk examines the disk's reservation status.
If the disk's reservation status shows that the disk is reserved, Clusdisk sends a single device reset.
If Clusdisk detects changes in the disk's signature when the disk comes online, or during arbitration of the disk, the signature field in the disk parameters is automatically updated.

Clusdisk behaviors for disks that do not support unique IDs

For disks that do not support unique IDs, Clusdisk and the disk resource use disk signatures to identify disks. This is the same method of identifying disks that is used in the original release version of Windows Server 2003. However, in Windows Server 2003 SP1 and in x64-based versions of Windows Server 2003, Clusdisk includes the following improvements to disk identification by using disk signatures:

Clusdisk now has a new disk signature cache. This cache stores all the known mappings between disks and their signatures. This cache is continuously updated. To update this cache, Clusdisk hooks in to the typical disk Input Output Control (IOCTL) function calls that return disk signatures.
Clusdisk optimizes searches for a disk by using the disk signature cache. In this scenario, Clusdisk first searches for a disk signature in its disk signature cache. If the disk signature is found, Clusdisk immediately returns with a success result. If the disk signature is not found in the cache, Clusdisk only searches for disks whose signatures are unknown. Additionally, Clusdisk only searches for disks that are valid for clustering. For example, Clusdisk does not search for non-small computer system interface (SCSI) disks, for system disks, or for CD-ROM drives.
On a device-reset request, Clusdisk only sends the device reset if the disk reservation status query returns a result of TRUE. This helps reduce the chance of Clusdisk sending a bus reset if disk hardware has failed.

When a new hard disk is brought online on a server cluster that supports the new Disk Unique ID feature, the following steps are performed:

During the procedure to bring the disk online, the disk resource tries to read the DiskUniqueIds parameter of the disk resource.
Because this parameter is not present on the new hard disk, the Clusdisk disk resource reverts to reading the disk signature to bring the disk online.
As a last step before online process is complete, the disk resource queries Clusdisk to determine the disk's unique IDs.
If the disk supports the Disk Unique ID feature, Clusdisk returns the disk's unique IDs. If the disk does not support the Disk Unique ID feature, Clusdisk returns a "not supported" result.
If the disk resource obtains the disk's unique IDs, the disk resource stores those unique IDs in the Cluster registry subkey location.
If the disk supports the Disk Unique ID feature, all subsequent online operations of that disk use the stored unique disk IDs.

Technical support for Windows x64 editions

Your hardware manufacturer provides technical support and assistance for Microsoft Windows x64 editions. Your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation with unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with your Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware.

For product information about Microsoft Windows XP Professional x64 Edition, visit the following Microsoft Web site:

http://www.microsoft.com/windowsxp/64bit/default.mspx

For product information about Microsoft Windows Server 2003 x64 editions, visit the following Microsoft Web site:

http://www.microsoft.com/windowsserver2003/64bit/x64/default.mspx

For product information about SCSI Primary Commands - 3 (SPC-3), visit the following Technical Committee T10 for SCSI Storage Interfaces Web site:

http://www.t10.org/ftp/t10/drafts/spc3/spc3r23.pdf