HP B6960-96035 - Manual (Page 291)

The example of the hardware provider is disk array, which has its hardware
mechanism of providing point-in-time state of a disk. A software provider operates
on physical disks and uses software mechanism for providing point-in-time state on
a disk. The system provider, MS Software Shadow Copy Provider, is a software
mechanism, which is a part of the Windows Server 2003 operating system.
The VSS mechanism guarantees that all hardware providers will be offered for creating
shadow copy before all software providers. If none of them is able to create a shadow
copy, VSS will use the MS Software Shadow Copy Provider for the shadow copy
creation, which is always available.
Data Protector and VSS
The Volume Shadow Copy service enables coordination among the backup
application, writers, and shadow copy providers during the backup and restore
process.
Figure 89 on page 292 and Figure 90 on page 292 show differences between the
traditional backup model and the model with the VSS coordinator.
Concepts guide 291