How Recovery Storage Groups Work in Exchange Server 2003


Topic Last Modified: 2005-07-12

Before you begin using recovery storage groups, you should have a general understanding of how they work and what their limitations are.

Recovery storage groups were designed to aid in database recovery under the following conditions:

  • The logical information about the storage group and its mailboxes remains intact and unchanged in Microsoft® Active Directory® directory service.

  • In addition, you need to recover a single mailbox, a single database, or a group of databases in a single storage group. Recovery scenarios include:

    • Recovering deleted items that a user mistakenly purged from their mailbox.

    • Recovering or repairing an alternate copy of a database while another copy remains in production (typically, with the goal of merging data between the two databases using the Mailbox Merge Wizard (ExMerge) tool.

    • Recovering a database on a server other than the original server for that database. If needed, you can then merge the recovered data back to the original server (although performance would be slower than if the recovery storage group and the original database were on the same server).

Use the following guidelines for working with recovery storage groups:

  • The database you are recovering must be on a server that is a member of the same administrative group as the server running the recovery storage group (if the database is from a different administrative group, the restore operation will not succeed).

  • If you want to recover more than one database at a time, you can add multiple databases to the recovery storage group as long as they are all from the same original storage group (once you have added the first database, you can only add databases from that database's storage group). Otherwise, you must use more than one recovery storage group (on more than one server).

  • The database you are recovering is from a server running a version of Exchange that is between Microsoft Exchange Server 2000 Service Pack (SP) 3 and the version of Exchange running on the recovery storage group server.

    All databases restored to the recovery storage group will be upgraded to the database version currently running on the recovery storage group server. This means that you cannot copy databases back to their original servers without first upgrading the original servers to the same version of Exchange (major version and service pack revision). Nonetheless, you can use ExMerge to move data between servers, regardless of version mismatches.

    In addition, databases from versions of Exchange later than the version on the recovery storage group server cannot be restored to the recovery storage group.

Recovery storage groups are not appropriate under the following conditions:

  • You need to recover public folder content. Only mailbox recovery operations are supported. Public folder recovery procedures remain the same for Exchange Server 2003 as they are for Exchange 2000.

  • You need to restore entire servers.

  • You need to restore databases from multiple storage groups.

  • You are in an emergency situation that requires changing or rebuilding your Active Directory topology.

In addition, you cannot use a recovery storage group if the Exchange configuration data stored in Active Directory has changed since the database was last backed up. The functionality of a recovery storage group depends on specific mailbox and mailbox database attributes in Active Directory. (Later sections of this section describe these attributes in greater detail). Because of this limitation, you cannot use recovery storage groups in the following circumstances:

  • You need to recover mailboxes that have been deleted or purged from the system, or moved to other databases or servers.

    Re-creating a deleted mailbox is not useful in this situation because Exchange does not recognize the re-created mailbox as the same mailbox. When you create a mailbox for a user, it has a unique identifier. If you delete and then re-create a mailbox, the mailbox will have a new identifier that is different from the previous identifier. For more information about these identifiers, see How the Recovery Database Links Back to the Original Database.

    You can use recovery storage groups in a limited fashion when you need to recover deleted or purged mailboxes. For more information about this situation, see Recovering Deleted Items or Purged Mailboxes Using a Recovery Storage Group in Exchange Server 2003.
  • You cannot use a recovery storage group to recover an Exchange database that was backed up using the Volume Shadow copy APIs. Exchange data that is backed up using the Volume Shadow copy APIs must be restored using the Volume Shadow copy APIs.

  • The database holding the mailboxes that you are trying to recover was moved to a different storage group after the last backup or has since been deleted.

    Re-creating a deleted database will not resolve this situation for reasons similar to those that apply to a re-created mailbox. Each database also has a unique identifier, and in Exchange, a re-created database is a new database with no relation to the previous database.


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