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What Is Virtual Disk Service?

Updated: March 28, 2003

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

In this section

For Windows 2000, each company that made storage devices (for example, hard disks, PCI RAID adapters, storage arrays) provided its own application for installing and managing that storage device. As a result, users had to run separate applications for each type of storage device they used on their computer system. This made managing the different types of storage devices difficult. To address this issue, Windows Server 2003 introduced Virtual Disk Service (VDS). VDS is a set of application programming interfaces (APIs) that provides a single interface for managing disks. VDS provides an end-to-end solution for managing storage hardware and disks, and for creating volumes on those disks.

VDS uses two sets of providers to manage your storage devices. The built-in VDS software providers enable you to manage disks and volumes at the operating system level. Hardware providers supplied by the hardware vendor enable you to manage hardware RAID arrays.

Each hardware vendor writes a VDS hardware provider that translates the general-purpose VDS APIs into specific instructions for their hardware. VDS simplifies storage management because storage applications no longer need to take into account the specific hardware being targeted. Because of VDS, you no longer need to use a different storage application to manage each different storage device. Instead, you can use one compatible storage application to manage any hardware that has a VDS hardware provider.

Windows Server 2003 components that work with VDS include the Disk Management snap-in, the DiskPart command-line tool, and the DiskRAID command-line tool (Diskraid.exe), which is available in the Windows Server 2003 Deployment Kit. DiskRAID requires at least one VDS provider supplied by a storage vendor.

Depending on the underlying disk subsystem, a disk can be a single physical hard disk (sometimes called a spindle), or it can be a group of hard disks bound together at the controller level and presented to the operating system as a single disk. This type of disk is often referred to as a virtual disk or logical unit number (LUN), and typically uses some form of hardware-based RAID to ensure data availability if one of the disks fails.

If your hardware vendor supplies a VDS hardware provider, you can use DiskRAID to manage individual physical disks, also called drives, in a LUN. The following example shows two DiskRAID printouts. The first printout shows information about the LUNs in a given disk subsystem. The second printout shows information about the physical disks that correspond to LUN 0.

How DiskRAID Displays LUNs in a Disk Subsystem

LUN ###  Status      Health        Type        Size    Sub  Dev
-------  ----------  ------------  --------  --------  ---  ---
LUN 0    Online      Healthy       Stripe     1064 GB    0    3
LUN 1    Online      Healthy       Parity      200 GB    0    4

How DiskRAID Displays the Disks Associated With LUN 0

Drive ###  Status      Health          Size      Free    Bus  Slot  Flags
---------  ----------  ------------  --------  --------  ---  ----  -----
Drive 0    Online      Healthy          66 GB     66 GB    0     5
Drive 1    Online      Healthy          66 GB     35 GB    0     0
Drive 2    Online      Healthy          66 GB     35 GB    1     0
Drive 3    Online      Healthy          66 GB     66 GB    1    11
Drive 4    Online      Healthy          66 GB     66 GB    0     7
Drive 5    Online      Healthy          66 GB     66 GB    0     8
Drive 6    Online      Healthy          66 GB     35 GB    1     3
Drive 7    Online      Healthy          66 GB     66 GB    1     7
Drive 8    Online      Healthy          66 GB     35 GB    0     2
Drive 9    Online      Healthy          66 GB     66 GB    1     9

Windows Server 2003 supplies VDS software providers for basic and dynamic disks and volumes so that you can use tools such as the Disk Management snap-in and DiskPart command-line tool to manage LUNs. However, the Disk Management snap-in and the DiskPart command-line tool display LUNs as disks, as shown in the following figure. Unlike DiskRAID, you cannot use these tools to view or manage the underlying physical disks in a LUN. However, using the Disk Management snap-in or DiskPart command-line tool, you can create partitions and volumes, convert disks to dynamic, and so forth. In the following figure, disk 2 (volume G:) and disk 3 (volume H:) are both on LUNs.

How Disk Management Displays LUNs As Disks

Disk Management

Common Virtual Disk Service Scenarios

VDS is commonly used in the following scenarios.

Managing LUNs on Hardware Storage Devices

VDS defines a set of features which provide a virtual view of any storage hardware. You can use the VDS APIs to write a storage management application that can manage any other storage hardware RAID arrays and LUNs that have VDS providers. For example, you can use the VDS APIs to create or delete simple, spanned, striped, mirrored, or striped with parity LUNs.

Managing Disks and Volumes

The VDS APIs enable applications to manage disks and volumes. You can create your own application that uses the VDS APIs or use applications such as the Disk Management snap-in or the DiskPart command-line tool (both use the VDS APIs) to perform tasks such as creating or deleting simple, striped, spanned, mirrored or RAID-5 volumes, formatting volumes, assigning drive letters to volumes, and converting basic disks into dynamic disks.

Managing End-To-End Storage Operations

The VDS APIs enable applications to manage end-to-end storage operations. Using the VDS APIs, your application can create a LUN in the storage array, unmask the LUN to a host, create and format a volume on the LUN, and assign a drive letter to the volume.

Technologies Related to Virtual Disk Service

VDS is closely related to the following technologies:

Volume Shadow Copy Service (VSS)

The Volume Shadow Copy service provides an infrastructure for creating consistent point-in-time copies known as shadow copies. The Volume Shadow Copy service can produce consistent shadow copies by coordinating with business applications, file-system services, backup applications, and storage hardware.

Logical Disk Manager (LDM)

The Logical Disk Manager (LDM) provides the drivers and user-mode components that are used to configure dynamic disks and volumes on computers running the Windows XP, Windows 2000, and Windows Server 2003 operating systems.

Virtual Disk Service Dependencies

VDS has the following dependencies:

  • OEM Hardware Providers. VDS requires a hardware provider that is supplied by the hardware manufacturer in order to manage storage hardware.

Related Information

The following resources contain additional information that is relevant to this section.

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