# System State Backup Behavior and Restore Limitations for Windows File System Backups

System state data contains Windows configuration information that is required to restore operating system functionality. Understanding how system state data behaves during backup and restore operations helps you determine what can be restored, what can be filtered, and how component failures affect backup jobs.

System state data is categorized in two ways:

- Components and services, which determine restore behavior.

- Critical and non-critical components, which determine backup behavior.

## How system state restore works

Restore capabilities vary depending on the type of system state data that you restore.

Restore type | Supported restore destinations
--- | ---
Entire system state | In-place and out-of-place
Individual system state components | Out-of-place only
Individual services | In-place and out-of-place

### Content indexing catalogs

Content indexing catalogs are restored only when you restore the entire system state. They can't be restored individually.

## How component failures affect backup jobs

System state components are classified as either critical or non-critical.

This classification determines whether a backup can successfully protect the information that is required for operating system recovery.

### Critical components

Critical components are required to restore a functional operating system.

If a critical component can't be backed up:

- The system state backup job fails.

- The backup doesn't contain sufficient information for system recovery.

Critical components can't be excluded from a system state backup.

If you attempt to filter a critical component, the operation fails with the following message:

    Critical system state components cannot be filtered from subclient configured to perform system state backup operation.

### Non-critical components

Non-critical components are part of the system state but aren't required for the operating system to start.

If a non-critical component can't be backed up:

- The backup job completes with errors.

- The failed component isn't available for restore.

## Filtering considerations

When you configure filters for Windows file system backups, consider the following limitations:

- Critical system state components can't be filtered.

- Some system state data can be restored only as part of a complete system state restore.

- Restore behavior varies by component type.

- Application-specific content protected through VSS writers might not be filtered exactly as expected because content selection is determined by the application writer.

## Technical reference

### System state components

System state components represent operating system configuration data.

Examples include:

- System file protection catalog and files

- Performance monitor configuration files

- Active Directory

- Quotas

- SYSVOL (for domain controllers)

- Certificate Services database (for certificate servers)

- Cluster database (for clustered servers)

- Registry

- COM+ database

- File Server Resource Manager (FSRM)

#### Restore behavior

- Restoring all components together supports:

- In-place restore

- Out-of-place restore

- Restoring individual components supports:

- Out-of-place restore only

### System state services

System state services represent data that is associated with Windows services.

Examples include:

- DHCP

- WINS

- Event logs

- Disk quota information

- RSM database

- WMI database

- Terminal Server Licensing database

- Content indexing catalogs

#### Restore behavior

Services can be restored:

- Individually or together

- To an in-place destination

- To an out-of-place destination

Exception:

- Content indexing catalogs

- Restored only when the entire system state is restored

- Can't be restored individually

### Critical components

The following components are classified as critical:

- Active Directory

- ASR

- Cluster database

- Registry

- System info archive

- System protected files

- System volume

- Offline files

- One Touch files

### Non-critical components

Examples include:

- BITS service

- Certificate Services

- COM+ database

- Content indexing catalogs

- DDR explicit content

- DFS Replication services

- DHCP

- Disk quotas

- Event logs

- File Server Resource Manager (FSRM)

- IIS

- Metadata

- NPS database

- Performance Counter

- Remote Storage database

- RSM

- Terminal Services Licensing

- UDDI database

- WMI database

- WINS

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