This topic
provides information using Exchange writer for the Windows Volume Shadow
Copy Service
to develop
applications for Exchange.
Introduction
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.
Caveats
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  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 | |
