Microsoft System Center Data Protection Manager (DPM) overcomes many limitations of traditional tape backups. You
can run DPM backups much more frequently than tape backups, which are generally performed nightly, while DPM backups are often performed hourly.
Furthermore, DPM retains multiple versions of each file that has been backed up. Users can even restore deleted or overwritten files themselves without bothering you, the administrator, and restore times are nearly instantaneous.
Data Protection Manager works by examining how a file has changed since the last time it was backed up, and then copying changes to the DPM server (only the bytes that have changed are copied, not the entire file; this saves space on the server).
One major drawback of Data Protection Manager is that it does not natively support Exchange Server backups. An online version of Exchange cannot be backed up with DPM because the files change too rapidly for DPM to keep up.
Theoretically, it's possible to use Data Protection Manager to do an offline backup of Exchange Server, but you would have to make sure that Exchange Server was offline before DPM performed any backup, which would lead to periods of inaccessibility and create the potential for errors. The bottom line is that offline Exchange Server backups using DPM just aren't practical.
Of course, where there's a will, there's a way. If you really want to use DPM to protect Exchange Server, there is a workaround that makes it possible. The trick to making the process work is to use NTBACKUP (or some other Exchange-aware backup application) to back up your Exchange servers up to a file; then use DPM to protect that backup file.
The Exchange DPM backup process
The location of your Exchange DPM backup file is important to the reliability of the process. First, you must configure the NTBACKUP location so that it places the backup file somewhere with a fast hard disk and a lot of free disk space (enough to accommodate your Exchange Server databases and then some).
Also -- and this is the most important one -- the backup location must be a part of the DPM protection group. Otherwise, DPM will be oblivious to your Exchange Server backups.
You also need to configure NTBACKUP to overwrite the existing backup file each time an Exchange Server backup is performed. Remember, Data Protection Manager copies changes to a file, not the entire file. So, if you simply appended backups within a single file, you would burn through a whole lot more disk space than if you simply replaced the file. Both methods allow you to recover multiple versions of the backup though.
Protecting your Exchange DPM backups
When it comes to protecting your Exchange Server backups with Data Protection Manager, timing is everything. Therefore, you should time the duration of the backup process.
Once you know how long NTBACKUP takes, add a little time to the estimate to accommodate for future database growth. Use the time you have calculated in conjunction with the backup's start time to figure out when the backup will complete. Then configure DPM to make a shadow copy an hour after the backup completes. You need to wait at least one hour so DPM has time to synchronize the changed data prior to the creation of the shadow copy.
While you are scheduling your first shadow copy, configure a second shadow copy to occur at least five hours after the first shadow copy is taken. For example, if your backup completes at midnight, you could schedule the first shadow copy for 1:30 a.m. and the second shadow copy for 6:30 a.m.
Performing Exchange DPM backup consistency checks
Along with the shadow copies, you also have to schedule some consistency checks in order to avoid file corruption. For the purposes of this tip, I am assuming that your consistency checks complete in less than four hours. If that isn't the case, then you will have to adjust the times provided.
With that in mind, you should set the first consistency check to occur at least an hour after the first shadow copy completes, but at least four hours prior to the second shadow copy.
While you're at it, set the maximum duration for the consistency check to four hours (this option is available in the Advanced Options section of the DPM console).
I know that the schedule is a little complicated, so let's recap:
- Back up Exchange Server with NTBACKUP.
- Wait at least an hour after the backup completes, then let DPM perform a shadow copy.
- Wait another hour and launch a consistency check.
- Finally, wait four hours and perform another shadow copy.
Don't be surprised if you receive error messages. They occur because DPM assumes that the replication cycle used to protect the backup file was invalid. Not to worry though -- that's why we perform the consistency check and second shadow copy.
If you require more detailed instructions regarding this process, you can find them in Microsoft Knowledge Base article 909644, How to use Microsoft System Center Data Protection Manager 2006 to help protect an Exchange server.
About the author: Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Exchange Server, and has previously received Microsoft's MVP award for Windows Server and Internet Information Server (IIS). Brien has served as CIO for a nationwide chain of hospitals and was once responsible for the Department of Information Management at Fort Knox. As a freelance technical writer, Brien 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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Related information from SearchExchange.com:
- Tip: Sample batch file script to run NTBACKUP on Exchange Server
- Tip: NTBACKUP caveat for Exchange Server and system state backups
- FAQ: Exchange Server backup and recovery
- Crash Course: Backing up Exchange Server with VSS
- 10 tips in 10 minutes: Fundamentals of Exchange Server disaster recovery
- Learning Guide: An administrator's guide to Exchange backup and recovery
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