Windows DFS users may notice that their incremental or differential backups are nearly as large as their full backups.

When using Windows DFS, you can also use a replication feature. This replication can potentially “touch” every file or nearly every file.

Thus, when using CFA to backup the volume, our software may think every file or nearly every file has changed.

This makes incremental and differential backups about the same size as the full backup.

While it’s possible to disable DFS Replication, most admins will be very reluctant to for many reasons.

Steps to resolve

Enable Preserve Access Times and Only Check Modification Times on both the file set and the inclusions. This minor change results in a much more reasonable incremental size.

The backups will only include new files and files that have been modified and ignore the updates made by DFS Replication (or by sharing certain public folders, etc.).