Introducing VSS Support › How VSS Support Works › Shadow Copy Creation Methods

Shadow Copy Creation Methods

There are two methods to create shadow copies: making a full copy (or clone) of all data on the volume or making a copy of only the data and files that have changed (known as copy-on-write). The method used to create the shadow copy and where the shadow copy is created are specified by the Provider associated with a volume.

• Hardware-based Providers are supplied by a disk array hardware vendor or storage virtualization provider (for example, XIOtech, HDS, EMC, and HP), and work only with their own arrays.
• Software-based Providers that use the copy-on-write method have been developed by a variety of vendors to instantly create a shadow copy of file systems. In some cases, applications like Microsoft Exchange Server 2003 use this method for high-performance, low-impact backup or duplication.

The Agent for Open Files uses the system Provider included with Windows Server 2003. This Provider uses a copy-on-write scheme to create shadow copies. If a hardware provider is installed, the Agent for Open Files uses it to create a full shadow copy of the entire volume. When the Enterprise Option for VSS Hardware Snap-Shot and a hardware provider are installed, the full shadow copy created is also transportable.