Windows Backup: What It Includes

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Microsoft has included a backup utility with Windows for the last several years. VERITAS Software Corporation (www.veritas.com; Mountain View, California) wrote the backup applets for Windows NT 3.1, 3.5x, and 4.0, as well as Microsoft Exchange Server and Microsoft Small Business Server. VERITAS later provided the backup applet for Windows 2000. Windows XP Professional also has a backup utility, and one can be installed for XP Home Edition, although it is not part of the default installation. This product backs up and restores encrypted files and folders without decrypting them, so there is no breach of the security protocols.

For Windows 2000, however, things operate a little differently. Only administrators or backup operators with access to a domain controller can backup any file or folder within the domain, except system-state data, provided a two-way trust relationship exists. Local group administrators and backup operators have the right to backup any file or folder on their local server, and anyone with administrative rights to that machine can backup a workstation running Windows 2000 Professional. System-state data (registry, boot files, Active Directory database, etc.) can only be backed up locally.

The backup utility performs five different types of backups:

• Normal — Using the normal setting backs up all selected files and folders, whether or not they have been previously backed up. It clears all previous backup markers (archive bits) and creates new ones for all files showing they have been backed up. Doing this type of backup can be slow, but the restoration process is faster than when the other backup methods are used. This method would be useful when there is no shortage of time to perform the backup, but it is desirable to get the device back on line as soon as possible after a failure.

• Copy — A copy backup also backs up all selected files and folders, but it does not reset any of the archive bits.

• Incremental — An incremental backup backs up all files or folders that have an archive bit. When done, it clears the markers so those files are not backed up again when the next incremental backup is done.

• Daily — As its name implies, a daily backup backs up all selected files and folders changed that day. It does not look at or reset the markers.

• Differential — Finally, with a differential backup, only those files and folders that contain a marker are backed up, but the markers are not reset. The differential backup takes longer than doing an incremental or daily backup, but the restoration goes more quickly. If you performed a full backup over the weekend, the differential backup would contain all files created or modified since then. By doing a normal backup and then daily differential backups, only these two files would be needed for restoration, whereas if a daily or incremental backup is done, each of those backups done since the last normal backup would be needed to do a restore. So, if a disk went down on Thursday, you would need the normal backup plus each of the incremental or daily backups from Monday, Tuesday, and Wednesday.

The main backup types used are normal, incremental, and differential (see Exhibit 1).

Exhibit 1: Backup Types

Backup Type	Advantages	Disadvantages
Full (normal)	Easy to schedule Easy to restore Removes transaction log files Circular logging	Can degrade performance Time consuming Requires a lot of tape space and a large number of tape replacements
Incremental	Little impact on server performance Removes transaction log files Minimal tape space	More complex restore process Circular logging turned off
Differential	Little impact on server performance Easy to restore Minimal tape space	Does not remove transaction log files Circular logging turned off Requires more tape space than incremental backup but less than full backup

To back up Windows 2000's Active Directory (AD), the normal backup method is used. When the AD is backed up, Windows Backup also automatically backs up all the system components and distributed services AD depends on, including the system startup files, the system registry, the class registration database of COM+ (an extension to the Component Object Model), the File Replication service (the SYSVOL directory), the Certificate Services database (if installed), the Domain Name system (if installed), and Cluster service (if it is installed). The directory by itself cannot be backed up.

Third-party software may contain additional methods to supplement the five types of backups used by Windows Backup. VERITAS Backup Exec, for example, includes an application called Working Set. This method backs up all files created or modified since the last normal or incremental backup. In addition, the administrator can specify a number of days back, and Working Set will backup all files accessed within that time period.

Obviously, one size does not fit all when it comes to backups. Most organizations will want to use a variety of methods to provide the optimum security and performance for their specific storage and operational needs, as well as methods geared toward their unique architectures. The built-in Windows utility provides basic backup functions and may be adequate for small installations, but most organizations will find the tool too limited. In this case, they will need to use a full-featured product such as VERITAS' Backup Exec or Computer Associates' BrightStor/ARCServe Backup.

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