Volume Shadow Copy Service (VSS) is a Windows service that allows users and applications to create snapshots, or “shadow copies,” of volumes or files. These snapshots help protect data by allowing recovery of previous versions of files or entire volumes.
Purpose of VSS
VSS enables backups and restores without disrupting system operations. It ensures that users can access data even while it is being modified.
- Helps in data recovery by creating backups without affecting system performance.
- Supports backup software and other applications like system restore.
- Offers the ability to restore files from earlier states.
How VSS Works
VSS creates shadow copies by coordinating with the file system and backup software. It ensures consistency by freezing the state of the system or volume at a specific point.
- VSS uses writers to ensure data consistency.
- Shadow copies are created at a specific point in time, capturing a snapshot.
- VSS can be triggered manually or by scheduled tasks like backups.
Key Components of VSS
VSS consists of several components that work together to create and manage shadow copies.
- VSS Requestor: The application or service that requests a shadow copy, such as backup software.
- VSS Writer: The component responsible for ensuring data consistency during a shadow copy. Examples include file system writers and database writers.
- VSS Provider: Manages the creation of shadow copies and works with storage devices.
VSS Process Flow
- The VSS Requestor requests a shadow copy.
- The VSS Writer prepares data for consistency.
- The VSS Provider creates the shadow copy.
- The VSS Requestor accesses or backs up the shadow copy.
Types of VSS Providers
There are different types of VSS providers, each playing a role in managing and creating shadow copies.
| Type | Description |
|---|---|
| System Provider | Built into Windows and used for standard file-based backups. |
| Hardware Provider | Provided by storage devices like SANs and NAS for hardware-based snapshots. |
| Software Provider | Created by third-party backup software for specialized backups. |
Benefits of VSS
VSS provides several advantages in data management and backup.
- Minimizes downtime: Allows backups without interrupting system operations.
- Data consistency: Ensures files are not corrupted during the backup process.
- Flexible recovery: Facilitates restoring specific versions of files or volumes.