Volume Shadow Services (VSS) on WHS


Windows Home Server uses Volume Shadow Services (VSS) to support Previous Version functionality for files stored in Shared Folders on the home server. The Home Server normally triggers a snapshot every 12 hours, enabling users to access previous versions of files stored in Shared Folders on your home server. This is archived through the Previous Versions functionality available in Windows client operating systems introduced with XP with SP1, Server 2003 and in all releases of Microsoft Windows thereafter.

What is VSS?

The feature VSS, also known as Shadow Copy or Previous Versions takes snapshots of files and folders either on a scheduled basis, or at the request of a program.

What is it used for?

VSS has several uses. First, it can be used by a program to “freeze ” the state of all files on a disk in order to get a consistent slice while other programs are potentially writing to the disk. This is particularly useful for software like backup programs, as it is very important that a backup be consistent in order for a restore to be successful. Second, it can be used to take a snapshot of a file at a point-in-time, in order to roll back to that point to a later date. This allows “undoing” a change, such as modifying or deleting a file or folder. This is called “Previous Versions” functionality.

What about Windows Server?

The WHS backup tool uses VSS on a client PC in order to obtain a consistent slice as described above. On the server, VSS is used in the shares to support the ability to “roll back” changes in the shares.

What about the recent FAQ posting

it turns out that there’s a bug in the way VSS is handled on servers with two or more drives. On such servers, it’s possible that “Previous Versions” will be shown, but will be inaccessible or a “Cannot copy <filename>: Invalid file handle” error message will be displayed when attempting to copy or restore a previous version of a file or folder.

There’s also a loosely related bug which only affects HP and other OEM servers. Because of the way the servers are prepared for duplication, VSS is turned off when they are shipped from the factory.

What can be done by WHS users?

Microsoft is aware of this problem and are researching it. While it’s possible for a user to turn on VSS, it’s probably not desirable because of the issue with multi-drive servers. For the time being, a WHS user should be aware of the issue, and not rely on “Previous Versions” functionality on the server.

Remember that the issue only occurs if certain conditions are true (see the FAQ: Previous Versions for files on Windows Home Server Shared Folders may not function correctly on the WHS Forum by Ken Warren).

If VSS is turned ON, how do I turn it OFF?

On the HP MediaSmart Server VSS is turned off for all partitions. To turn it off on other hardware you will need to Remote Desktop into your Home Server and start regedit. (WARNING: If you don’t know what regedit is, then do not follow these guidelines as you could render your WHS inoperable)

Open the following location in the registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Home Server\Storage Manager\Volumes

You will find a GUID for each volume. Turn it off by setting the SnapPeriod key for that volume to 0 from the default 43200000 (milliseconds is 12h) . By default, it’s only enabled for the D: partition.

Finally a re-boot of the server will be required.

Many thanks to fellow WHS MVP Ken Warren for additional information for this article.

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Comments (8)

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  1. Arnoud says:

    What kind of server system is WHS when it cannot deal with data reliably in so many ways? I just bought a WHS server and am seriously peeved after reading stories like this, incl. the other data corruption bug with multiple harddrives. I bought it mainly as a data backup solution, but I cannot use it for that.. unbelievable that these things stay unfixed for months with systems as critical as this. Way to go Microsoft..!

  2. Casey says:

    Microsoft Fanboi’s are just working behind the scenes to orchestrate “independent” praises to offset their own proven fundamental flawed WHS Drive Extender technology.

    READ For Yourself the Unfolding Story…
    “WHS: A Series of Unfortunate Events”

  3. Greg Martin says:

    So, as I have an HP MediaSmart I don’t need to worry about this VSS bug – but does that also mean I won’t suffer from the ‘multiple hard drives’ bug? Are the two (or three!) related?

  4. Raymond L. says:

    The VSS bug is another bug NOT related to the WHS Drive Extender bug. Only, I wouldn’t call the later a bug, it’s data corruption!

  5. Greg M. says:

    Thanks for clarifying. Without wishing to get philosophical why is data corruption not a ‘bug’?

  6. Casey says:

    Software bugs refers to a glitch, a mistake, a defect or flaw in a design in the software code, right?

    However, anyone experiencing KB 946676 “data corruption” doesn’t get Microsoft to recover their now corrupted and destroyed files! No patch here!

    Microsoft has stated on many occasions that it’s WHS Drive Extender code is just an algorithm of a “sort” that’s just needing to be adjusted. Whatever you want to call that, only Microsoft knows.

    But, bugs are normally something that’s suppose to be workout before the operating system becomes operational. That’s why we pay good money to have testing done first, so customers don’t become testers but end up as software users, for which everyone pays to for that experience expectation.

    What’s so shameful yet, is in how Microsoft obviously failed to address this reported issue during the beta period. Which Microsoft had claimed some 100,000 beta testers reportedly had used this software product.

    And if that wasn’t bad enough, despite having the 100,000 beta testers which many of them had reported this issue, Microsoft didn’t resolve the issue even after going public last year and continues to sell a proven damaging software product that everybody must take many steps to avoid using the product in order to avoid destroying their data, financial files, family videos, photos with corruption.

    If it’s just a bug, why does it take so long to offer a patch, that is unless your re-writing the fundamental underlying code that’s needing to be replaced.

    Bugs, don’t require re-writing the foundation. There just to patch not offer a new version to replace. Imagine a flaw in your automobile, would you call it a bug if the dealership gave you a new automobile in it’s place?

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