Be wary of Shadow Copy limitations

If you're dealing with shared folders, Shadow Copy can make your life easier. But it's not a complete backup solution.

Because it allows quick restores of damaged or deleted files, the Shadow Copy feature in Windows Server makes life easier for storage administrators dealing with shared folders.

One of the nice things about Shadow Copy is that it doesn't carry much of a performance penalty while the Shadow Copies are being made. "Not much", it's worth noting, is not the same as none. In a heavily-loaded server, it is worthwhile to set aside a disk for Shadow Copies, in order to eliminate extra head seeks.

However, Microsoft cautions there are limits to the way Shadow Copy is used. Shadow Copy isn't intended as a complete backup solution for shared folders. For example, while Shadow Copy does make copies of DLLs (Dynamic Link Libraries), it is not recommended to use those copies to recover DLLs in case of emergency.

Microsoft also warns against using a Shadow Copy to back up disk image. Although Shadow Copy will recursively recover all the files in a volume, it doesn't delete files. That means it doesn't restore the disk as it was at the time the Shadow Copy was made. It is also slow for large quantities of data. Microsoft suggests restoring the image from backup media instead.

Microsoft has a FAQ on using Shadow Copies of shared folders at:
www.microsoft.com/windowsserver2003/techinfo/overview/scrfaq.mspx.

For more information:

Tip: Eight guidelines to Windows-based snapshots

Tip: Resource guide to snapshots (or point-in-time copies)

 


About the author: Rick Cook has been writing about mass storage since the days when the term meant an 80K floppy disk. The computers he learned on used ferrite cores and magnetic drums. For the last 20 years, he has been a freelance writer specializing in storage and other computer issues.
 

This was first published in June 2004

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