Volume Shadow Copy Service

What Does Volume Shadow Copy Service Mean?

Volume Shadow Copy Service (VSS) is a set of Component Object Model (COM) interfaces in Microsoft Windows that provide the framework for doing volume backups and for creating consistent, point-in-time copies of data (known as shadow copies). Business applications, backup applications, fast-recovery solutions, file system services and storage hardware are put into coordination so that VSS can produce consistent shadow copies. The technology requires the use of the New Technology File System (NTFS) for creating and storing the shadow copies. VSS was first introduced in Windows XP, and shadow copies can be created on local or external volumes.

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Volume Shadow Copy Service may also be known as Shadow Copy or Volume Snapshot Service.

Techopedia Explains Volume Shadow Copy Service

Shadow copies are created namely by two methods: Complete copy or differential copy. Both methods result in two data images: original volume and shadow copy volume. Original volume has full read/write access, while shadow copy only has read access rights.

The complete copy method makes a full copy of the data on volume, either through hardware or software methods. The differential copy method makes use of blocks, which store the new changes that are done to the original volume. A buffer is then used to logically construct the shadow copy. The differential copy method aids in creating the shadow copies rapidly as it’s only writing the changes. However, in order to restore data, the original data volume needs to be present all the time.

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Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.