Data Protection and Disaster Recovery Tips

Using the Wrong Backup Method

The two basic methods for backing up Exchange data are online and offline. Online backups use a Microsoft interface (such as Extensible Storage Engine -- ESE, backup APIs, or Microsoft Volume Shadow Copy Service -- VSS) to copy the selected Exchange data while the Exchange services are running and while the target database is mounted and active. The Exchange-provided APIs back up transaction logs and truncate the logs when necessary.

Offline backups copy the Exchange database and log files while the database isn't mounted. Some solutions purport to copy Exchange data without using Microsoft's APIs but also without dismounting the databases. The Microsoft article "XADM: Hot Split Snapshot Backups of Exchange" (http://support.microsoft.com/?kbid=311898) explains that Microsoft considers these backups to be offline.

Performing online backups is preferable for typical production operations because online backups capture a consistent copy of the Exchange databases without interrupting user access. However, offline backups are useful in some situations. For example, performing a complete offline backup of your Exchange database and logs is a good idea before installing a Windows or an Exchange service pack or performing a forklift upgrade of the database to another server. Although creating offline backups is more time consuming than generating online backups, many administrators prefer the extra safety of having a periodic offline backup in addition to routine production backups.
 

Not Verifying Backups

If your backup fails and no one notices, does it make a sound? Maybe not, but your users will surely sound off if you can't recover their mail data. I recently worked with a company whose administrator accidentally corrupted a mailbox database. When the Exchange administrator tried to restore the database, he discovered that backups of the database had been failing for more than four months because the administrator hadn't installed the Exchange version of the company's third-party backup agent software. The installed version of the agent tried to back up the files but couldn't because the Exchange Information Store (IS) had the files open. Even a cursory review of the backup software's reports or the Application event log would have shown that the software wasn't backing up the Exchange data. Unfortunately, no one monitored the backups for success.

To prevent this problem, regularly check your backup software's logs. You need to verify:

If one of these three checks fails, you should be able to determine the cause of the backup failure and therefore fix the problem. For example, during an online backup, Exchange computes a checksum for each page and compares it with that page's checksum on disk. If the checksums don't match, you receive a 1018 error and the backup stops. Checking your backups would alert you to the error and give you a chance to fix it before the backup stopped.

Even if your backups are working now, don't get complacent. Changing your environment, backup software, Windows configuration, or Exchange configuration might make your backups fail in the future. Check your backups regularly for the best protection. The fastest and simplest way to check your backups to be sure they work is to check the Application event log and the report that your backup program generates. Check the Application event log to ensure that Exchange didn't generate any errors during the backup period. Check the backup program report to verify that the backup program didn't skip any files and that no errors occurred.