In many organizations, disk-to-disk-to-tape backup is replacing the traditional disk-to-tape backup systems that have been the standard for disaster recovery for many years. A big part of that reason is Microsoft's new server product, Microsoft System Center Data Protection Manager (DPM).
In a disk-to-disk backup, data is copied not to a backup tape but instead to a share point on one of the servers on your network. The tape portion of the disk-to-disk-to-tape backup comes in when the network share containing the backup is backed up to tape.
From that description, the idea of disk-to-disk-to-tape backup sounds redundant. In its simplest form, disk-to-disk-to-tape backups are not very practical. However, DPM makes disk-to-disk-to -tape backups not only practical, but desirable. In fact, I use DPM to back up my own network.
Microsoft System Center Data Protection Manager addresses backup issues
The reason I like Microsoft System Center Data Protection Manager is because it addresses many of the shortcomings of traditional backups, such as backup frequency. Most organizations back their data up late at night, which leaves a lot of room for data loss. Imagine that some bigwig in your company created a file at 9 a.m. for a meeting late that afternoon. But at 11 a.m., something caused that file to be destroyed.
The person who created the file calls you and demands that you restore the file from backup. Unfortunately, you have to tell them
Microsoft System Center Data Protection Manager can resolve this situation. When you deploy DPM, you designate which volumes or shares on your network should be protected. At that time, Data Protection Manager makes a full backup of all of the files in the protected share or volume. From that point on, whenever files are created or modified, DPM backs them up. In fact, you can even configure DPM to run backups hourly.
Now, let's go back to the bigwig who deleted that file he needed for that afternoon's meeting. If Microsoft System Center Data Protection Manager runs hourly backups, the file will have been backed up -- even though it was only created recently. Not only that, there is even a user interface that allows users to perform their own restores without having to call you, the admin! Since the backup is disk-based, you don't even have to load a tape.
Now, having a massive hard disk storing multiple versions of every file on your network sounds great, but what about the practicality of doing so? Rest assured, DPM is designed to prevent the backups from draining your network of resources.
Sure, the initial backup can take quite a while to complete and it consumes as much disk space as you would expect it to. But as files that have been previously backed up are modified, the file is not re-copied to the DPM server; only the bytes in the file that have changed since the last backup are copied. This saves disk space on the DPM server and network bandwidth as well. (If you're still concerned about the impact of DPM on your network, Data Protection Manager does have a bandwidth throttling feature.)
Another problem with traditional backups: In most cases, files that are open are not backed up. Shadow copy has made it possible to back up open files, but many backup applications, especially older ones, do not take advantage of shadow copy. But since DPM is fully shadow-copy-compliant, it can back up files whether they are open or not.
Other Microsoft System Center Data Protection Manager features
That DPM offers continuous data protection and allows users to restore their own files is nice, but what really sold me on the product was its speed and reliability. How many times has a user asked you to restore a file that they need for a meeting in ten minutes? When this happens, you would normally have to figure out which tape the data is on, mount the tape and then wait for the file to be restored. Then there's always the chance that the tape could be unreadable, the data could be corrupt or the tape drive could eat the tape during the restore operation. These things happen.
DPM allows users to restore their own data, but suppose this particular user either doesn't know how to do this or doesn't have the necessary permissions. So it's up to you to do the restoration for them. That being the case, you'll be glad to know that restores are handled through a console that resembles Windows Explorer. The process of restoring a file is simple -- and extremely fast.
Tapes are linear in nature, so when you restore a file from tape, you have to wait for the tape to scroll to the correct location. Disks offer random access, so the read head can go straight to the file that needs to be restored without having to read through every other file on the disk first. Since the backup is disk-based, you also do not have to worry about the tape being eaten, getting lost or being damaged or stolen.
One last thing worth mentioning is your constantly shrinking window for backup. Each day your servers contain more data than the day before. But so many companies are turning into 24/7 operations that administrators are often being asked to back up huge amounts of data during a tiny window of time each night.
With Microsoft System Center Data Protection Manager, this is no longer a problem, because Data Protection Manager backs up files automatically all day long. Since files can be open during these backups, users are not disrupted. The users never even know that the backups are taking place. At some point in time, you will want to back the DPM server up to tape, but this can be done at your leisure without fear of disrupting the users.
Microsoft System Center Data Protection Manager Fast Guide
Verifying Data Protection Manager status
Server plays key role in Data Protection Manager deployment
Why Data Protection Manager is replacing disk-to-tape backups
Troubleshooting Data Protection Manager warning message
Measuring the impact of Data Protection Manager 2006
Storage pool savvy helps admins optimize Data Protection Manager
Watch for unsupported data types in Data Protection Manager
Protecting servers with Data Protection Manager
About the Author:
Brien M. Posey, MCSE, is a Microsoft Most Valuable Professional for his work with Windows 2000 Server and IIS. He has served as CIO for a nationwide chain of hospitals and was once in charge of IT security for Fort Knox. He writes regularly for SearchWinSystems.com and other TechTarget sites, and has also written for Microsoft, CNET, ZDNet, MSD2D, Relevant Technologies and others.
This was first published in March 2006