Virtual Disk Service

[Kody Chavva]

Beginningwith Windows 8 and Windows Server 8, the Virtual Disk Service COM interface is superseded by the Storage Management API, a WMI-based programming interface. For managing storage subsystems, (Windows) disks, partitions, and volumes, we strongly recommend using the Storage Management API. For more information, see the Windows Storage Management API.

For all usages except mirror boot volumes (using a mirror volume to host the operating system ), dynamic disks are deprecated. For data that requires resiliency against drive failure, use Storage Spaces, a resilient storage virtualization solution. For more information, see Storage Spaces Technical Preview.

Application developers who use the interfaces described in this guide can query and configure a heterogeneous set of vendor-supplied and internally managed storage. VDS hides from applications the complexities associated with storage, making the service both vendor and technology neutral.

VDS is supported on Windows Server 2003, Windows Vista, and later. For information about run-time requirements for a particular programming element, see the Requirements section of the documentation for that element.

VDS is available in the Microsoft Windows Software Development Kit (SDK). You can install the SDK for Windows 7 and Windows Server 2008 R2 from the Windows Download Center. This version of the Windows SDK can be used to develop VDS applications for Windows Server 2003, Windows Vista, and later. You can also download the ISO version of the SDK from the Windows Download Center.

Virtual Disk Service is a Microsoft Windows service that performs query and configuration operations at the request of end users, scripts, and applications. The service extends the existing storage capabilities of Windows Server operating systems in the following ways:

VDS defines three interfaces: a single interface between the application layer and the service, and two interfaces between the service and provider programs in the data layer. The following illustration shows the application-to-service boundary and the service-to-provider boundary.

N-tier architecture enables VDS to coordinate with the file-system functions, synchronize provider activities, and arbitrate between applications. Being between the application and provider, VDS presents uniform functionality to applications even though some the underlying providers might lack such uniformity.

A software provider is a host-based program that is supported by a kernel-mode driver in the storage I/O stack. The provider-kernel runtime interacts with the Mount Manager at boot time or the Plug and Play (PnP) Manager at discovery time to claim each disk. Software providers operate on volumes, disks, and disk partitions.

VDS includes two provider types. The basic software provider manages basic disks and offers no fault-tolerant binding. The dynamic software provider manages dynamic disks and offers fault management where applicable. Software-provider behavior is consistent with the behavior of basic and dynamic disks on the host. For example, if the operating system of a given host supports fault-tolerant dynamic disks, VDS also supports this behavior on the host.

The capabilities of a hardware provider depend on the capabilities of the underlying hardware. Consequently, the degree to which each manufacturer implements the API can vary. For example, manufacturers can include additional methods to optimize configurations, monitor and dynamically tune performance, automate fault management, or provide other beneficial functionality.

Hardware providers offer several configuration options that are not available to the software providers. Most notable is the automagic configuration model, which presents an attribute-based view of storage to each application. Binding hints, such as "mostly reads" or "fast crash recovery required" replace the complexity of binding physical storage into virtual storage. Each hardware provider performs extent mapping, space allocation, and binding-type selection based on the hints that are submitted by an application. For the complete hardware provider description, including the configuration options, see the documentation that is supplied by the subsystem manufacturer.

Typical applications for VDS solve configuration management and monitoring problems, and range from dedicated storage-management systems to back-office applications seeking better control over configuration or fault management. The following applications use VDS today:

Hi @Neil Cooper I have a few questions. Are these media agents physical or virtual? Would you be able to get one VM using the stable vmtools version (please make sure you are not using version 11269 issue reported here ( -Tools/11.0/rn/VMware-Tools-1105-Release-Notes.html)

Hi Neil,

Have you checked that Automount is disabled and the SAN policy is OfflineShared on the affected Media Agents?

Is there any AV on the Media Agents that could be scanning the attached disks or interfering with the CV Processes?

As I navigate down the internet researching this issue I sure see some other very similar cases. So what I`m about to share it may (not) be totally connected to your issue, so take all of this with some grain of salt.

So again, Im not an expert in Dell Compellent, but after reading some of these docs I do wonder if you have the software configured with the VSS on your media agents. Would you be able to review the links and confirm here?

This is an old document from Dell on their - CommVault Simpana 10 Best Practices for the Dell Compellent Storage Center and though the articles in my previous post do mention the requirement Compellent Replay Manager Service on Hyper-V - it raises the question as to whether or not you have Dell Compellent Software Replay or any other software that may be interfering with the way Intellisnap works when it takes the snaps and mounts on your Media Agent during an snapmount.

In any case, if you do have it installed, check out the version as some older versions may not support integrate well (or integrate at all) with Commvault. From what I could find, it seems version 8.0.1 is the latest.

If you do have replay manager, make sure to be using the latest version as it fixes issues with the VSS Provider, if you have the latest version and still does not work, try removing it completely and retry the operation.

Hi, to me the fact that you see multiple LUNs and dead paths has a lot to do with the MPIO software and the Dell Compellent Software I mentioned above. Check it out and let us know when you have a chance. Enjoy your weekend.

I`m quite unsure as to what your thought process is here or even at what your questions are. Previously shared some links that points to best practices as well as a software for the Media Agents, did you have a chance to look at that?

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