Boswell's Q&A

Volume Shadow Looms Large

Gotchas from readers who've implemented Windows' Volume Shadow Copy Service.

• By Bill Boswell
• 05/10/2005

Bob Wilson, who works for Computer Sciences Corporation, submitted a heads-up on an issue that he discovered. In brief, he says that if you right-click a Dfs folder in a Terminal Server session, you may not see a Previous Versions tab even though the Previous Versions client has been installed on the terminal server. This happens if the Dfs root is hosted on a Windows 2000 Domain Controller or a Windows Server 2003 Domain Controller that does not have the Shadow Copy for Shared Folders feature enabled. A patch for this problem is available in a hotfix at KB article 887189: "The Previous Versions tab for a file or for a folder in a DFS share is not displayed in Windows Server 2003 and in Windows XP."

Ron Rynbrandt, who works for the Dr Pepper 7UP Bottling Group, wrote:

We use VSS for shared folders, and we love it. I store all of my Citrix user folders and profiles on a server where I use VSS as a restoration tool. It replaces about 95 percent of all restores we perform, and reduces restoration times from 2-3 hours (from tape) to about five minutes. We do restrict usage of VSS restores to just IT people as part of our change control process.

One small caveat: When I first set up VSS, I let it use unlimited space on the drive. This worked okay for a while, until the drive got close to full. Then, when the VSS service ran again, it ran out of disk space and corrupted all VSS images on the drive. This happened a couple times before I set a limit on VSS space to 5 MB less than the capacity of the drive. Now, VSS images are handled in a FIFO order correctly.

Falco Dam, who works for IT-to-IT, a training and consultancy company in The Netherlands, had several important items to watch out for when deploying VSS:

I have worked with VSC in several environments and would like to point out another few gotchas for those people considering to implement this cool feature.

Volume shadow copies can only be enabled on an entire volume. If at all possible, try to find out what data would need VSC and place that on a separate volume. You do not want, e.g., roaming profiles hogging up your precious VSC space.

You can only set the amount of space reserved for VSC, not the number of shadow copies. How many shadow copies you can go back, therefore, depends on the activity on the volume. I've found it quite difficult to predict up front the number of saved shadow copies you will have available at any one time; you only know when you've implemented it. A tip would be to hold open the possibility to assign more disk space to VSC if needed.

You always run the (albeit minimal) risk of overwhelming the Volume Shadow Copy Service, which causes all of your shadow copies to be deleted. This risk can be mitigated by placing the VSC data on a separate spindle of disks, making sure you have enough resources, and installing SP1 which includes KB 833167 as you've pointed out. Still, you need to be aware of this risk.

Any backups you make (using NTBackup or any other tool) will only back up the current data. There is no way that the shadow copies themselves can be backed up (none that I know of, anyway). You may want to consider redundancy in the spindle that you use to hold the VSC data.

As for the Previous Versions client, I am always wary to just install it on any workstation. I'd hate to see some clueless user playing with it and restoring a massive folder from a shadow copy with a single click. There's just no way to undo this damage. My advice is to install the Previous Versions client on administrators' computers only and perhaps some power users.

Thanks to Ron, Bob, and Falco and to everyone who writes in with great information to share with the readers of this column.