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When Exchange crashes, an otherwise normal day can quickly turn into one of the worst days of your life. It can take several hours to bring an Exchange server back online, and it never fails that some busybody from management wants to check up on you or threaten you every five minutes.
Prior to Exchange Server 2003, this was simply par for the course. There was no high-speed Exchange disaster recovery technique. But with Exchange 2003, you can perform a partial recovery using the Dial Tone Method, so that users can continue to send and receive mail while you are restoring the old messages.
There will be a couple of times during this recovery process when users will momentarily lose Exchange connectivity, but they will be interrupted far less than if they had to wait around all day for a restore from backup tape.
If your Exchange server is completely destroyed during some catastrophe, but the rest of your network is functional, here's how you can implement this recovery technique.
Step 1: Bring a new Exchange server online and restore mailboxes
- Use Active Directory Users and Computers to remove the old domain server and each user's mailbox.
- Once you have selected all of the applicable accounts, right click on them and select the Exchange Tasks command.
- Follow the prompts to get rid of the mailboxes.
- The next step is to bring the new server online and install Exchange Server. Give the new server the same name as the old server, and make sure it's running the same version and service pack as the old server.
- After Exchange has been installed, go back to Active Directory Users and Computers and create mailboxes for your users. You create the mailboxes the same way you removed them: select all of the user accounts, right click on them and click the Exchange Tasks option.
- Now choose the Create Mailbox option and follow the prompts.
Step 2: Merge and restore the information stores
So far, you have managed to bring a new Exchange server online and create mailboxes for each of your users. Assuming that the new server is properly configured, users should now be able to send and receive mail. The trick now is to merge the old server's information store with the new server's information store. You accomplish this task using a Recovery Storage Group.
- Open the Exchange System Manager and navigate to Administrative Groups -> your administrative group -> Servers -> your server.
- Right click on your server and select New -> Recovery Storage Group to view the Recovery Storage Group properties sheet.
- Fill in the locations for the restored transaction logs and the system path. You can use any path you want, but the location must have enough free disk space to accommodate the information store that you will be recovering.
- Click OK to create the Recovery Storage Group.
- Now, right click on the Recovery Storage Group and select "Add Database To Recover" to see a list of all of the Information Stores present within your Exchange organization.
- Select the one that pertains to the information store that you will be recovering and click OK twice. After a brief delay, Exchange Server will create an information store beneath the Recovery Storage Group.
Important: Do not try to mount this new information store yet; doing so will disrupt the checkpoint files and cause a lot of problems.
The next step is to restore your information store backup. For right now, you should only restore the mailboxes. Do not attempt to restore public folders or log files at this time. You can restore them later, but only after you have gotten rid of the Recovery Storage Group.
- When you restore the mailboxes, restore them in the normal manner. The restored mailboxes will automatically be redirected to the Recovery Storage Group rather than the information store.
- After the restore operation is complete, go ahead and mount the mailbox store contained within the Recovery Storage Group. The mailbox store will initially appear empty, so refresh Exchange System Manager to display the recovered mailboxes.
Step 3: Swap databases and merge the data
Now you have the old versions of the mailboxes in the Recovery Storage Group -- but you also have the temporary mailboxes in the Exchange information store that users have been using to send and receive mail for the last few hours. You could just merge the mailboxes together and be done with it, but there are a couple of problems with this approach. First, if you have a big information store, the merge could take a long time. Second, merging the two information stores will cause problems with rules and OST files. A better solution is to swap Exchange databases and then merge the data.
- First, warn your users that the server is going to be unavailable for a while.
- Then, open Windows Explorer and navigate to the Recovery Storage Group's location.
- Create a folder named Save_Original.
- Now, use Exchange System Manager to dismount the information store and the Recovery Storage Group's database.
- Use Windows Explorer to move the Recovery Storage Group's .EDB and .STM files to the Save_Original folder.
- Go back to Exchange System Manager and delete the Recovery Storage Group's database. This will delete the logical database structure, but not the database itself.
- Return to Windows Explorer and navigate to the directory containing the information store.
- Create a folder named SaveDialTone.
- Copy the .EDB and the .STM files associated with the Information Store into the SaveDialTone folder.
- Now, go into the Exchange System Manager and change the path for the Information Store so that it points to the Recovery Storage Group's database path.
- Move the files that are in the Save_Original folder back to the Recovery Storage Group path.
- Go back into Exchange System Manager and right click on the information store.
- Verify that all the information is correct and then select the Database tab.
- Select the "This Database Can Be Overwritten By A Restore" checkbox and click OK.
- You can now mount the information store. The users will have access to all of their old messages.
- Go back to Windows Explorer and create a folder named DialTone next to the SaveDialTone folder.
- Right click on the Recovery Storage Group and select the "Add Database to Recover."
- Choose the information store that you are working on and click OK.
- In Properties, enter the path to the DialTone folder and click OK.
- Finally, move the files from the SaveDialTone folder into the DialTone folder and mount the Recovery Stoage Group database.
Step 4: Recover the mailboxes
The last step in the process is to recover the mailboxes. Before you do though, you must make sure that your Exchange server is running Exchange 2003 Service Pack 1. Otherwise, this technique will not work. If you can't install Service Pack 1 for some reason, then the workaround is to use ExMerge.
- To recover the mailboxes, select the mailboxes within the Recovery Storage Group's list of mailboxes.
- Right click on the mailboxes and select the Exchange Tasks option.
- When the Exchange Tasks Wizard starts, click Next, select the Recover Mailbox Data option, and click Next again.
- Verify the destination mailbox store and click Next.
- You must now decide whether you want to merge the restored data into the user's current mailbox or if you'd rather copy the contents of the restored mailbox over top of the user's existing mailbox. Use the Copy option because the Merge option will cause big problems since you have swapped databases.
- Click Next and you will be prompted to enter a data and time for which you want to run the recovery operation.
- Click Next again and the mailboxes will be restored.
- Click Finish to complete the operation.
About the author: Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. Brien has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. As a freelance technical writer he has written for Microsoft, CNET, ZDNet, TechTarget, MSD2D, Relevant Technologies and other technology companies. You can visit Brien's personal Web site at http://www.brienposey.com.
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This procedure sounds nice if you have another Exchange server that you can start up from scratch. But for those of us that only have one Exchange server and Windows Small Business Server 2003, this simply is not an option.
Additionally, if you want to use the ExMerge utility, you have to give the Installable File System (IFS) mapping for the drive a letter and change the default permissions for each user's folder -- and that takes additional time for the permissions to propagate.
—David M.
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