operating system and applications and freezes I/O to the storage system to allow snapshot creation (without the freeze function, data could become corrupted when the snapshot is taken because the system might be in the middle of a task). Meanwhile, applications continue to run uninterrupted.
The original volume continues to change as the process continues, but the shadow copy of the volume remains constant. VSS also gives permission to the backup application to access the volume and back it up in its frozen state. The shadow copy volume is then used for the actual backup. After VSS saves the shadow copy volume on the backup device, it deletes the shadow copy.
VSS coordinates between Requestors (backup applications such as Recovery Manager), Writers (applications such as windows services like Exchange 2007) and Providers (components that create the shadow copies).
Table 2 VSS Components
VSS Component | VSS Component Description |
Requestor | The requestor is backup software that initiates the creation |
| of the shadow copy. |
Writer | The writer is any application software that participates in |
| the shadow copy process and whose files and data are |
| included in the process. |
Provider | The provider is the storage technology that does the actual |
| shadow copy. |
Supported VSS Components
VSS components currently supported by HP 3PAR VSS Provider Software for Microsoft Windows include:
•Requestor
◦Recovery Manager
◦Symantec NetBackup for Microsoft Windows
◦HP Data Protector for Microsoft Windows
•Writer - Microsoft Exchange 2007