This documentation is archived and is not being maintained.

Exchange writer for the Windows Volume Shadow Copy Service

Exchange Server 2003

Exchange writer for the Windows Volume Shadow Copy Service

This content is no longer actively maintained. It is provided as is, for anyone who may still be using these technologies, with no warranties or claims of accuracy with regard to the most recent product version or service release. This topic provides information using Exchange writer for the Windows Volume Shadow Copy Service to develop applications for Exchange.


The Volume Shadow Copy Service (VSS) component of Microsoft® Windows Server™ 2003 coordinates the activities of providers, writers, and requestors for creating and using shadow copies. The VSS writer for Exchange Server 2003 enables applications to back up and restore Exchange storage groups that are stored on hardware that supports the VSS.


Backups using the Volume Shadow Copy service are performed at only the storage group level. Individual databases cannot be backed up. Restoring an individual database from a Volume Shadow Copy Service backup is supported; however the entire storage group must be offline during the restore. Although multiple Exchange storage groups can be backed up at a time using the Volume Shadow Copy Service, only one backup can be performed at a time.

Functional Criteria

Criteria Exchange Backup and Restore API
Application Domain Applications use VSS to back up and restore Exchange 2003 storage groups.
Major Objects Applications that use the VSS to back up and restore whole storage volumes use COM objects and interfaces that include the following: IVssAsync, IVSSBackupComponents, IVssComponent, IVssCreateWriterMetadata, IVssEnumObject, IVssExamineWriterMetadata, IVssWMComponent, IVssWMDependency, IVssWMFiledesc, IVssWriterComponents, IVssWriterComponentsExt.
Data access model Access to data inside a VSS shadow copy depends on the hardware vendor's implementation. Exchange should not be used to directly access the storage group data inside the shadow copy. The data must be restored to its original location before Exchange can mount the storage group.
Threading Models Single threading only. When an application uses VSS and the Exchange writer to back up or restore data, the code that accesses VSS and the Writer should be single-threaded. Applications should not use a multiple threads to access the VSS COM objects.
Application Architectures Backup and Restore applications that use VSS to back up Exchange 2003 storage groups typically consist of a background service that performs the backup, a scheduling service, and a Windows GUI application console that controls and configures the backup and restore system.
Remote Usage Applications that use VSS must run on the Windows Server 2003 computer on which the Exchange store process is running. Because of the flexibility in large storage systems, the hardware hosting the storage volumes might not actually be a physical part of the computer running Windows Server 2003.
Transactions No.
Management Capabilities Applications that use VSS can take advantage of the Windows Events and performance counters provided by VSS, the Exchange writer, and any that are provided by the VSS-compatible storage hardware vendor.
Availability VSS is a component of Windows Server 2003. The Exchange writer is installed when Exchange 2003 is installed on Windows Server 2003.

Development Criteria

Criteria Exchange writer for the Windows Volume Shadow Copy Service
Languages and Tools VSS can be used in any COM-compatible language. It is most frequently used in applications written in C++. Because creating shadow copies requires the Exchange store to be momentarily taken offline, backup applications are typically very time-sensitive, which in most cases prevents using languages like Visual Basic or VBScript.
Managed Implementation VSS cannot be used in a managed-code environment.
Scriptable Yes, but not recommended.
Test/Debug Tools No special tools are required to debug applications that use the Windows Volume Shadow Copy Service.
Expert Availability Finding developers who can effectively program VSS applications should not be difficult. Although relatively few developers have used VSS previously, the level of information and support from hardware vendors and Microsoft should enable most programmers to work with VSS. Because of the nature of the Backup and Restore API, programmers with experience creating high-reliability software are preferred.
Available Information For information about VSS, see the Exchange Server 2003 SDK and the Windows Development Online link Web site.
Developer / Deployment Licensing Refer to your Exchange and MSDN subscription licensing agreements to determine whether additional licenses are required for the Exchange 2003 servers that store the data backed up and restored by custom applications that use VSS.

Security Criteria

Criteria Exchange writer for the Windows Volume Shadow Copy Service
Design-Time Permissions The VSS infrastructure requires VSS requestors, such as backup applications, to be able to function both as COM clients and as a server. Requestors need to securely manage which COM clients are able to make incoming COM calls into its process. The requestor-specific security settings must allow outgoing COM calls from the requestor to the VSS service and writer processes.
Setup Permissions No special permissions are required to install applications that use VSS. Because the applications must run on the computer running Exchange, the account under which the application is installed must have sufficient permission to install software on that computer.
Run-Time Permissions A VSS requestor typically needs to be run under an account that is either a member of the Administrators built-in group or the Backup Operators group.
Built-in Security Features VSS requestor applications can use CoInitializeSecurity to set a process-wide permission check of default COM access. VSS writers can also be set to allow all process access to call into the requestor processes or set to allow only specific processes access to call into the requestor process. Additional registry settings can be configured to allow access to specific applications.
Security Monitoring Features There are no built-in security monitoring features.

Deployment Criteria

Criteria Exchange writer for the Windows Volume Shadow Copy Service
Server Platform Requirements VSS is only available when Exchange Server 2003 is running on Windows Server 2003.
Client Platform Requirements There are no special client requirements beyond the VSS core requirements.
Deployment Methods VSS applications can be installed on server computers using standard software distribution technologies.
Deployment Notes