Definition - What does Volume Shadow Copy Service (VSS) 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.
Volume Shadow Copy Service may also be known as Shadow Copy or Volume Snapshot Service.
Techopedia explains Volume Shadow Copy Service (VSS)
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.