Windows NT Backup Strategy

Could your business survive if you lost all the data in your Microsoft SQL Server database? What would be the impact of losing months of email from your Microsoft Exchange server? Unfortunately, backups tend to be low on the priority list until something bad happens, at which point all your users expect you to recover their data immediately. In this article, I look at the Windows NT backup program, consider some alternatives, and discuss factors that might influence your choice of backup strategy.

Backup Philosophies
You can take one of two approaches to backups: You can back up the server, or you can have users back up their workstations. When you back up the server, you typically back up everything on the server, including user files that you store there. The amount of data at stake in a system crash or a natural disaster is considerable, probably on the order of gigabytes. Therefore, you need a high-capacity tape drive or an alternative high-capacity system such as DVD-RAM—and of course, you must plan for off-site storage of the backup media. If restoration becomes necessary, you might have to restore the entire system, a task that could take some time.

The workstation backup approach is appropriate for the user who accidentally deletes a file or wants to use last week's version of a file instead of the current version. These situations usually involve a much smaller volume of data (maybe a few megabytes and often just a single file) than a system crash or major disaster. For backup protection at this level, you can equip users with some type of backup device, such as a Zip drive or LS-120 high-capacity disk drive, and trust them to use it. However, most users are not going to take time to perform backups. You are usually better off to require users to store their data on the server.

As a systems administrator, accept responsibility for backing up only data that is stored on the server and use a tape drive to back up the crucial portions of the system. You also might want to install some other backup device (e.g., DVD-RAM, CD-Rewritable—CD-RW) that offers instant access to files, and let your users use it for frequent backups of their data. If any users insist on keeping their data on their workstations, they also must take responsibility for their backups. This strategy means that the administrator (or whoever performs the backups) does not need to access the individual users' workstations. You thus maintain a high level of security.

The Price Is Right
NT comes with a built-in backup program (ntbackup.exe), which Screen 1, page 182, shows, that is sufficient for basic backups. However, this program lacks features that make it easy to configure, such as the ability to schedule backup tasks.

The NT backup program seems to have problems with building catalogs of the files it backs up, making restores more difficult than they need to be. (For more information about these problems, see the sidebar "The Mysterious Disappearing Tape Catalog," page 183.) Many administrators like to replace the NT backup program with a third-party product such as Cheyenne's ARCserve, Seagate's Backup Exec, UltraBac, or NovaStor. These products allow scheduling with various levels of flexibility and ease of use. However, each product entails additional cost and maintenance.

Do You Need an Agent?
The NT backup program cannot back up open files. Therefore, it cannot back up files such as SQL Server databases that are in use. Third-party programs typically offer agents, usually at extra cost, that can back up open databases. If you need to back up several Microsoft BackOffice applications, the additional cost for the agents can add up quickly. If you prefer to avoid the higher costs, another solution might work for you. For example, the backup option built into SQL Server can back up data to a disk file. Once the backup is complete, the backup file is no longer open—so you can back it up using any basic NT-based backup software. An additional benefit to this approach is that backing up to a disk file is faster than backing up to a tape, so this method minimizes the slowdown time for your database or messaging server.

SQL Server 6.5 has some scheduling capability, but SQL Server 7.0's scheduling capability is far better. SQL Server 7.0 lets you set up a sequence of jobs that perform the SQL Server backup to a disk file, then run a batch file to start the NT backup of that disk file to a tape drive.

File vs. Image Backups
A popular feature that the NT backup tool does not offer is image backup. NT (and many other software packages) backs up files individually and restores them the same way. Using this restoration method usually means you must reinstall the OS and the backup software, then perform the restore. An alternative that UltraBac and ARCserve offer is the option to perform an image backup. This method backs up the disk sectors to tape without regard to file delineation. The restore process then puts the sectors back on disk. With a set of boot diskettes, you can restore from a tape without having to reinstall NT. Both of these packages also let you extract a single file from the image backup, giving you the best of both worlds.