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Imagine that your Exchange server's primary hard drive dies and has to be replaced. If that server isn't part of a cluster, or if the drive isn't mirrored or part of some other type of fault-tolerant array, you've got a big problem.
In such a situation, the generally accepted recovery procedure involves installing Windows and IIS, updating Windows with whatever service pack was previously in use, and restoring the most recent backup.
Depending on the speed of your server and tape drive, this procedure could take anywhere from two to six hours -- that's a lot of downtime.
If the failed Exchange Server is running on Windows Server 2003 though, you can use Automated System Recovery (ASR) to greatly improve recovery time. With ASR, you don't have to wait for your Windows installation to complete before restoring your backup. Instead, you can restore the backup during the early phases of Windows Setup.
There are a few stipulations to using ASR:
- Your server must be running Windows Server 2003.
- The backup you restore must be an ASR backup. If you open NTBACKUP and click the Welcome tab, you'll see that the Automated System Recovery backup option is completely separate from the normal backup options. ASR will back up the Windows OS and system state. (It will also create an ASR floppy disk, which I explain in the next section.)
- ASR will not back up or restore Exchange Server or any other applications loaded on the server. ASR's sole purpose is to restore Windows quickly, so you can focus on getting your applications up and running sooner.
- When you run an ASR-based restore, ASR will format the system drive. This shouldn't be a problem is you are replacing a failed drive. But you want to avoid an ASR-based restore if there is salvageable data on the drive.
The ASR floppy disk
As a part of the ASR backup, ASR creates an ASR floppy disk. This floppy disk is used during the restore process to provide ASR with information about the backup media.
This floppy disk is required for an ASR restore. If you have misplaced it, you can create another one. Just take the server's backup tape to another machine and restore the ASR.SIF and ASRPNP.SIF files to a floppy disk. These files are located in the \Windows\repair folder.
Performing an Automated System Recovery
Now that you have your ASR floppy disk, it's time to perform the restore operation:
- Boot the server off the Windows Server 2003 installation CD.
- When Setup gives you the option of performing an automated system recovery, insert the ASR floppy disk and your backup tape.
- Follow the remaining prompts to restore your server.
Once the restore operation completes, you must install Exchange Server and return it to a useable state.
The first thing you should do is make sure that Windows is up to date. In order to successfully recover Exchange, Windows must be running the same service-pack level (and preferably the same hotfixes) as it was when the most recent Exchange backup was created.
Once Windows has been updated, you need to install Exchange Server. The easiest way to do this is to run Exchange Setup with the /disasterrecovery switch. This tells Setup to install Exchange Server with no databases, which greatly simplifies the recovery process. Once Exchange is installed, make sure you install the Exchange service pack that was in use prior to the crash.
At this point, you are free to restore your most recent Exchange backup. There are a couple of reasons why you had to wait until now to restore the backup. First, it wouldn't have done any good to have restored the databases previously, because Exchange wasn't installed. Second, you can only restore an online Exchange backup if the backup software is Exchange-aware. NTBACKUP doesn't become Exchange-aware until you install Exchange.
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 the 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, TechTarget, CNET, ZDNet, 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 was first published in September 2005