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Creating a usable Exchange backup requires utilizing a key Microsoft technology that allows for online backup of Exchange at the storage group level. These APIs are also referred to as the "ESE Backup APIs." Backup and storage vendors implement these APIs in their hot backup agents. One key function of these APIs is to properly "quiesce" the Exchange database so that all data is committed to disk. Then, the API allows for the data movement of the EDB, STM and associated logs. In this model, when the hot backup is done, the data files are encapsulated in the backup agent's tape format. From this backup, the data can be restored by sending it back through the ESE backup API.
There is also Exchange server clustering that provides another method for failover; however, it is not able to prevent logical corruption.
The ESE backup API, when running on Exchange 2003 and Windows 2003, provides new functionality in VSS (Volume Shadow Copy Services).
"The Volume Shadow Copy service coordinates communication between Requestors (backup applications), Writers (applications in Windows services like Exchange Server 2003, and SQL Server 2000), and Providers (system, software or hardware components that create the shadow copies). To use the Volume Shadow Copy service feature to backup Exchange Server 2003, the backup program must include an Exchange Server 2003 aware Volume Shadow Copy service requestor. Because the backup program that is bundled with Windows Server has no such requestor, organizations must use third-party backup applications."
These VSS hardware and software requestors can provide the appropriate calls to create an Exchange consumable snapshot, as it was properly quiesced, and move the data appropriately. For more information see KB article 822896. .
Bottom line: Without the use of this API, there is no Microsoft supported way of moving the file-level data safely. Be wary of third mirror break-off solutions that do not utilize the aforementioned technology. These would provide data that is application-inconsistent and would require both physical (ESEUTIL) and logical (ISINTEG) repair prior to use, and cannot guarantee data preservation.
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More information from SearchExchange.com:
20 tips in 20 minutes: Protecting and recovering Exchange 2003 data
Reference Center: Exchange Server backup and recovery
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