Key Features and Concepts:Point-in-Time Snapshots:
- Shadow copies capture the state of files and volumes at a specific moment in time, creating read-only copies of data.
- Shadow copies use a copy-on-write mechanism, ensuring that the original data remains untouched while changes are recorded in the snapshot.
- Shadow copies capture only changes made after the last snapshot, minimizing storage requirements and backup times.
Volume Shadow Copy Service (VSS):
- VSS relies on snapshot providers (software or hardware) to manage the creation and maintenance of shadow copies.
Benefits:Quick Data Recovery:
- VSS coordinates snapshot creation, ensuring applications and services are quiesced before capturing the snapshot.
- Shadow copies enable users to restore previous versions of files and folders without relying on traditional backups.
Low Impact on Performance:
- Only incremental changes are stored in shadow copies, minimizing the storage space required.
- The copy-on-write mechanism has minimal impact on system performance during snapshot creation.
Use Cases:Accidental File Deletion:
- Users can restore files and folders on their own, eliminating the need for IT intervention in many cases.
File Version Recovery:
- Users can restore files they've accidentally deleted or modified incorrectly.
- Restore previous versions of files if they've been overwritten or modified in an undesirable way.
Quick File Retrieval:
- In case of data corruption, shadow copies can provide clean copies of files before the corruption occurred.
Setting Up Shadow Copies:Enable Shadow Copies:
- Users can retrieve files without relying on IT personnel or complex backup restores.
Schedule and Storage:
- Navigate to the properties of a volume and enable shadow copies in the "Shadow Copies" tab.
Recovery and Access:
- Configure the schedule for creating shadow copies and specify the maximum storage space they can occupy.
- Users can access previous versions of files by right-clicking a file, selecting "Properties," and navigating to the "Previous Versions" tab.
- While shadow copies are more storage-efficient than traditional backups, they still consume disk space over time.
How Volume Shadow Copy Service Works
- Regularly manage shadow copy retention settings to prevent excessive storage consumption.
A complete VSS solution requires all the following basic parts:
1. VSS service
: Part of the Windows operating system that ensures the other components can communicate with each other properly and work together.
2. VSS requester
: The software that requests the actual creation of shadow copies (or other high-level operations like importing or deleting them). Typically, this is the backup application. The Windows Server Backup utility and the System Center Data Protection Manager application are VSS requesters. Non-Microsoft® VSS requesters include nearly all backup software that runs on Windows.
3. VSS writer
: The component that guarantees we have a consistent data set to back up. This is typically provided as part of a line-of-business application, such as SQL Server® or Exchange Server. VSS writers for various Windows components, such as the registry, are included with the Windows operating system. Non-Microsoft VSS writers are included with many applications for Windows that need to guarantee data consistency during back up.
4. VSS provider
: The component that creates and maintains the shadow copies. This can occur in the software or in the hardware. The Windows operating system includes a VSS provider that uses copy-on-write. If you use a storage area network (SAN), it is important that you install the VSS hardware provider for the SAN, if one is provided. A hardware provider offloads the task of creating and maintaining a shadow copy from the host operating system.How a Shadow Copy Is Created
This section puts the various roles of the requester, writer, and provider into context by listing the steps that need to be taken to create a shadow copy. The following diagram shows how the Volume Shadow Copy Service controls the overall coordination of the requester, writer, and provider.