The Provider is responsible for managing the volumes involved in the shadow copy backup, as well as for creating the shadow copy. The Provider interfaces with the shadow copy creation capabilities that are either part of the operating system (software-based) or on the disk array (hardware-based).
The Windows Server 2003 operating system has a built-in (system) Provider that uses a copy-on-write scheme to create the shadow copies. It can create shadow copies of any NTFS, FAT32, or RAW volume on the Windows Server 2003 system. The system provider only creates shadow copies on NTFS. Third-party Providers are also available.
Hardware disk array vendors can supply their own Providers to interface with the VSS framework, and direct where and how to create the shadow copies.
The Agent for Open Files works with the Windows Server 2003 system provider, but if a hardware-based provider is available, it is used instead. When the Enterprise Option for VSS Hardware Snap-Shot is installed, hardware-based providers work with VSS to create a transportable shadow copy.
There are two types of Providers:
Typically implemented as a DLL and a filter to manage storage. The shadow copies are created by software. Shadow copies created with this type of Provider include a point-in-time view of the original volume as it existed before the shadow copy, and the subsequent shadow copies of only the changed data.
Are implemented at the hardware level and work with a hardware controller or storage adapter. Shadow copies are created by a storage appliance, host adapter, or RAID device outside the operating system. Shadow copies created with a hardware-based Provider are of an entire volume (a full copy), and are typically mirrored views of the original volume. Additionally, if a transportable shadow copy is created, it can be imported onto other servers within the same system.
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