Exchange Backup and Recovery Architecture
The main components in the system are Microsoft Windows Server 2008 (providing the Volume Shadow Copy Service), Microsoft Exchange Server 2010 (and the Microsoft Exchange Server 2010 writers for the Windows Server 2008 Volume Shadow Copy Service), and the third-party (or custom) backup/restore application (including the requestor and the provider).
The VSS communicates with the Windows Server 2008 file system and with the mass storage device driver through a third-party (or custom) provider. It is up to the hardware provider to determine where the shadow copy of the storage group will be created. The VSS abstracts the hardware-specific shadow copy so the backup/restore application can access the shadow copy in a uniform manner without knowing the hardware implementation details.
The backup/restore application is also called the VSS Requestor. The requestor communicates with the VSS to obtain information about Exchange 2010, to command the creation of shadow copies, and to gain access to the data for backup.
The Exchange store is a component of Exchange 2010 and accesses Exchange 2010 databases through the Windows Server 2008 file system. Within the file system, each Exchange server can simultaneously mount up to 100 databases with their accompanying database (.edb) files, transaction log files, and a checkpoint file.
To support the VSS, Exchange 2010 includes an Exchange writer that is built into the Exchange store. The Exchange writer coordinates with the Exchange store (operating on behalf of the requestor) to freeze and dismount the database before backing it up, and then to unfreeze and mount the database after the backup is complete.
During a restore, the backup/restore application instructs the Exchange writer to coordinate with the Exchange store (operating on behalf of the requestor) to dismount the database, replace the database files, mount the database, and then replay the transaction logs (as needed).
When restoring, the requestor also communicates with the VSS to prepare the system for the restore, and then to put the data back onto the mass storage device. The backup/restore application is also responsible for working with Windows Server 2008 to read data from and write data to the backup storage media, whether a tape archive, a storage area network, or other backup medium.
The restored database can be mounted either as a regular, active database, or as the Exchange 2010 Recovery Database. Only one mounted database can be designated as a recovery database on each Exchange server.
Information required to successfully complete backup and restore operations among Exchange Server 2010, the VSS, and the backup/restore application is transferred as part of the Exchange writer metadata.