ContinuousDataReplicator Disaster Recovery Solution for Building a Standby Exchange Server

Overview

Configuration

Bring the Standby Server online

Overview

This document describes the procedure necessary to enable rapid recovery of Production Exchange Server on the Standby Server using ContinuousDataReplicator (CDR). This procedure involves pre-configuring Exchange Server on the Standby Server to eliminate these steps during an actual disaster recovery, reducing the recovery time.

This procedure uses the Standby Server as the target. However, an intermediate server could also be used as the CDR target. The diagram depicts the configuration used in this approach. In addition to using the live replicated data, this procedure also uses Consistent Recovery Points (CRPs) to allow for alternative recovery points in the event the live (replicated) data can not be used by Exchange Server due to consistency issues.

This procedure has been validated using Exchange 2003 on Windows 2003 with SP1. Newer versions of Exchange should behave the same in these scenarios.

Advantages

ContinuousDataReplicator provides a mechanism for asynchronously replicating file system and application data to a remote site. Data is replicated at the byte and file level which provides for a very effective use of available network bandwidth, thus making it ideal for disaster recovery scenarios.

Configuration

The configuration described in this document involves setting up CDR to replicate to the Standby Exchange server directly. The Standby Exchange machine will replace the production machine by assuming its name but keep its existing IP address. The original DNS entry for the Standby Exchange Server will remain but the IP address for the Production Exchange Server will be set to the IP address of the Standby Server.

The following sections discuss preparing the Production and Standby Servers as well as setting up replication.

Prepare the Production Server

It is assumed that the Production Exchange Server (alpha) is operational and up to date with respect to service packs and/or required patches. Also, it is assumed that the Standby Exchange Server (venus), which is also the CDR target, is running as a member of the domain and that the CommServe has already been installed.

The following steps should be followed to prepare the Production Exchange Server for CDR:

  1. Make sure that the storage groups are moved off of the C: drive. This is usually the case in production environments but the location should be verified.
  2. Place the system path on the same volume as the transaction logs. This will make the configuration of the replication pairs simpler since the .chk file and the logs will be collocated.
  3. Install ContinuousDataReplicator on the server along with the Windows File System iDataAgent and the Exchange DB agent. It is expected that standard backups will be executed on the Production Exchange Server to manage the logs. Note that CDR will not truncate Exchange logs since all backup operations associated with CDR are file system based. This means that although a CRP will quiesce Exchange and provide for a consistent point in time view, there is no knowledge of the application during the backup phase. Hence, the Exchange APIs which truncate logs are not utilized. Note that as the Exchange DB backup causes logs to be truncated on the production server the deletion of the log files will be replicated to the target by CDR, so cleanup will be automatic on the target server.

    If using the Exchange DB agent is not possible on the Production Exchange Server then circular logging can be enabled to manage log growth.

Prepare the Standby Server

Configuring the Standby Exchange Server will require that the Production Exchange Server be offline while working on the Standby Server. These steps could be performed during the recovery time, however, that would increase the recovery time and potentially introduce more opportunity for error. It is recommended that these steps be performed in advance to provide the most straight forward recovery procedure. If the Standby server is being created at recovery time then skip all steps which are performed on the production server.

On the Standby Exchange Server (venus)

  1. Install ContinuousDataReplicator software.
  2. Create volumes and folders for storing Exchange data and logs equivalent to those on the Production Exchange Server. These will be used for replication targets for the live data as well as operational data and logs locations when the Standby Exchange Server is being used.

On the Production Server (alpha)

  1. Set the following services configuration, if they are not already set:
  2. Stop the following Exchange Services, and set the Startup Type to Manual:
  3. Stop All running Exchange Services.
  4. Rename the Production Exchange Server to a temporary name (oldalpha).
  5. Reboot the Production Exchange Server so that the new name takes effect.

    At this point Exchange will be off-line and the Standby Server  can be configured.

On the Standby Exchange Server (venus):

  1. Rename the Standby Server (venus) to original Production Exchange Server (alpha).
  2. Reboot the Standby Server. The Standby Server is now alpha.
  3.  Install the following Windows components, if they are not already installed:
  4. Create Partitions if necessary and folders to match the locations of the Exchange logs and databases on the production Exchange server.
  5. Install Exchange on the Standby Server from the command line using the /DisasterRecovery switch. Select the same components, in DisasterRecovery mode, that were installed on the Production server. (If this option does not exist, verify that the command line was entered correctly).

    Example: Z:> setup.exe /DisasterRecovery

  6. Apply the Service Pack(s) and patches that were applied to the production Exchange server.

    Example: Z:> update.exe /DisasterRecovery

    If Exchange won't allow you to run the update with disaster recovery, you most likely have a permissions problem. First, try running the update.exe command with /DomainPrep. After these changes have been made and replicated through the domain, you should be able to run the update.

  7. Make sure that all of the Exchange services are stopped.
  8. Set all the Exchange services to manual startup.

On the Domain Controller

  1. To enable the Exchange Services to start on the Standby Server, the Windows ADSI Edit tool must be installed. (See Microsoft KB article 325674). The tool can be installed on any server in the domain, but it is preferred to be installed on a Domain Controller. The ADSI tool is located on the Windows 2000/2003 Install CD. Once the tool is installed, you will need to set the appropriate permissions for the Standby Server. To start ADSI Edit click on Start => Programs => Windows Support Tools => ADSI Edit.
    1. In the ADSI Management console's left windowpane, expand the following:
      • Configuration Container
      • CN=Configuration
      • CN=Services
      • CN=Microsoft Exchange. 
    2. Right-click your organization [Domain Name] then click Properties. Click the Security tab:
      • Verify that the Standby Server object is there. (Production Server name) If the server object is not listed, click Add, select the server object, click Add, and click OK.
      • Highlight the server object and verify that the Allow check box for Create all child objects and Delete all child objects is selected. If they are not selected, click to select them, then click OK.
    3. In the ADSI Management console's left windowpane, expand the following:
      • CN=[Domain Name]
      • CN=Administrative Groups
      • CN=First Administrator Group
    4. Right-click CN=Servers and select Properties. Click the Security tab:
      • Verify that the Standby Server object is there. (Production Server name) If the server object is not listed, click Add, sort the objects by name, highlight the appropriate server object, click Add and click OK.
      • Highlight the server object and click Full Control under Allow, then click OK.
    5. Expand CN=Servers, right-click CN=Servers and select Properties. Click the Security tab:
      • Verify that the Standby Server object is there. (Production Server name). If the server object is not listed, click Add, sort the objects by name, highlight the appropriate server object, click Add and click OK.
      • Highlight the server object and click Full Control under Allow, then click OK.

On the Standby Exchange Server (alpha, previously venus)

  1. Manually start the Exchange services on the Standby Server.
  2. Verify that the Transaction Logs and System Path are located as they were on the Production Server using the Exchange System Manager.
  3. Also verify that the Stores and Public Folders are correctly located.
  4. Stop all of the Exchange services on the Standby server. Make sure to set all startup types to Manual.
  5. Rename the Standby Server back to its original name (venus) and reboot for the change to take effect. Check the Active Directory to make sure that it has been updated and that the Standby server is listed by its original name.

On the Production Exchange Server (oldalpha)

  1. The Exchange services on the Production Exchange Server can now have their Startup Types reset back to their original values.
  2. At this point the Production Exchange Server (oldalpha) can be renamed back to its original name (alpha) and rebooted.
  3. Using the Exchange System Manager mount the Mailbox and Public Folder stores on the Production Exchange Server (alpha).
  4. Verify that Exchange is operational and that email / public folders are accessible.

Setting up Replication

Now that the servers are prepared and the CommCell software has been installed, the replication set and associated replication pairs can be set up and replication initiated. The replication set and pairs can be either configured manually, or by the use of wizard. Though not required, when live replica data is used to bring up the Standby Exchange server - it avoids a Copyback operation. Note the destination paths on the target must be set to mimic the source. See ContinuousDataReplicator for more details on installation and configuration of CDR.

When the pairs are in sync and all of the initial data has been replicated to the target (venus), the next step is to schedule Consistent Recovery Points along with backups of those Recovery Points. This allows for Point-In-Time recovery for the Exchange Server with known consistent data. Alternatively, the live data can be utilized to provide the closest to up to the minute recovery. However, note that live data will be crash consistent at best and is not guaranteed to be recoverable by Exchange.

Bring the Standby Server online

The strategy for replacing the original Production Server with the Standby Server is illustrated below:

Because of the Exchange dependencies with Active Directory, changes are required for Exchange to operate correctly on the Standby Server.

  1. It is likely that the initiation of the fail-over to the Standby Exchange server is due to the Production Exchange Server crashing but in any case the production server (alpha) should be shutdown.
  2. On the Domain Controller  RESET the Production Exchange server computer entry. This forces the computer to rejoin the domain.
  3. Remove the Standby Exchange server (venus) from the domain and reboot. Removal from the domain and the associated name change appear to have to be done in two steps, which necessitates multiple reboots to get the complete switch to occur.
  4. On the Domain Controller using Active Directory Users and Computers delete the entry for the Standby Exchange server (venus).
  5. Rename the Standby Exchange server (venus) to the production Exchange server (alpha) and reboot.
  6. Rejoin the Standby Exchange server to the Domain as the production Exchange server (alpha) and reboot.
  7. Verify/Change the IP address of the Production Exchange server (alpha) to match the IP address of the Standby Exchange server (venus). By changing the IP address of the original Production Exchange server (alpha) to the Standby server�s address Outlook clients will be able to connect to Exchange correctly. Leave the existing entry for the Standby Exchange server (venus) intact so that the system can be accessed by its original name as well.
  8. At this point the live replica data can be used or a recovery point selected to recover Exchange. Note that live data is crash consistent at best and can pre-date the crash point in time due to the asynchronous nature of CDR. However it will provide the closest to current data for recovery purposes and not require a copy operation since it is in the proper location already. If recovery from the latest replicated data is not desirable or possible due to inconsistencies then a CRP or backup can be chosen instead. From the CommCell Console browse the CRPs and select the one to be utilized on the Standby server.
  9. Recovery of CRP data can be done two ways. (Use one method.)
    1. The Copyback button can be used to initiate the copy operation from the GUI. The original Standby Exchange server name (venus) is selected as the recovery host and the Copyback function is initiated. This is the most straight forward method.

      NOTE: The copyback will overwrite the live copy so be sure that the live copy will not be required in the future. Otherwise manually copy the data to a new location before issuing the Copyback function. After selecting the Standby Exchange Server by its original name (venus) click OK to start the copy operation.

    2. Alternatively the CRP could be mounted and manually copied to the required location. This is accomplished through the View Snapshots function. Click View Snapshots Each of the snapshots in the CRP will be listed and each should be mounted by selecting the individual snapshot and clicking the Mount button which exposes the mount point dialog so that a drive letter can be assigned.
  10. Start the Exchange services on the Standby Exchange server.
  11. Start the Exchange System Manager on the Standby Exchange server and mount all mailbox and public stores
  12. Verify that Exchange is operational and mailbox and public stores are accessible.
  13. Optionally, set the following Exchange services to Automatic and start these services. (This is advisable if the Standby Exchange server is expected to be operational for an extended period of time.)

    In addition the Do not mount this store at start-up option on the Mailbox and Public Store could also be un-checked so that the stores will mount automatically.

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