Microsoft's System Center DPM 2007 can perform backups of Exchange Server's transaction logs on a consistent basis...
(every 15 minutes). This is helpful for two reasons.
- Consistently occurring backups eliminate some of the problems associated with a volume failure. Suppose that the volume containing your server's transaction logs were to fail. If you performed a normal Exchange Server backup, you would lose any transactions that had occurred since you last backed up the server. If you're running one backup late at night, you may be losing several hours worth of data. If your transaction logs are backed up every 15 minutes, you probably won't lose more than a few minutes worth of data in the event of a failure.
- It frees Exchange Server from having to perform a monolithic backup late at night. This is important because Exchange Server is designed to perform a number of automated maintenance tasks late at night. These tasks are often performed simultaneous to the backup. While both of these operations can be performed concurrently, they tend to slow each other down considerably. This can prevent your backup from completing within the allotted time frame and can prevent automated maintenance tasks from completing at all.
For more information on some of the other benefits to using DPM 2007 to back up Exchange Server, I recommend reading Microsoft's DPM 2007 datasheet.
How does Microsoft's DPM 2007 work?
To understand how DPM 2007 backs up an Exchange Server, you must understand how traditional Exchange Server backups work. Normally, when transactions occur, they're written to the server's transaction logs, not to the database itself. When a transaction log fills up, another transaction log is created.
When an administrator performs an online backup, the first thing that happens is that the information store database is written to disk. While this is occurring, data is still being written to the transaction logs. When the database backup is complete, the current transaction log is closed -- even if it isn't full -- and a new transaction log is created. All of the closed transaction logs are then backed up and committed to the database. Next, committed transaction log files are truncated.
Data Protection Manager 2007 still deals with the transaction logs and the information store, but does it in a completely different way. When a DPM agent is initially installed on the Exchange Server, it creates a baseline copy of the Exchange Server. After that, two processes run in parallel to protect the server's data.
The first process is transaction log synchronization, which is performed according to the server's protection schedule. It can, however, occur as often as every 15 minutes.
The other process is an express full backup of the Exchange information store. This process uses the Exchange 2007 Volume Shadow Copy Service Writer (VSS Writer) to determine which blocks in the database have changed since the last express full backup. Those blocks are then copied to the DPM server. Only the blocks that have changed are copied, so the process completes more quickly and requires less space than it would if the entire database were being copied.
Data Protection Manager 2007 can accommodate up to 512 express full copies of an Exchange Server database. An express full backup is the equivalent of a normal online backup but doesn't require as much time and overhead as a normal online backup.
About the author: Brien M. Posey, MCSE, is a five-time recipient of Microsoft's Most Valuable Professional award for his work with Exchange Server, Windows Server, Internet Information Services (IIS), and File Systems and Storage. 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 website at www.brienposey.com.
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