Files in Single Instance Storage Replicate When Running NTBackup Against a Replicated Dfs Share

When you use the Microsoft Windows NTbackup.exe program to back up a Distributed File System (Dfs) share that is synchronized with the FRS (File Replication service), the replication process to the other partners occurs as the files are backed up.

This behavior can only occur with files that are backed up as Single Instance Storage (SIS) files. SIS is a feature that is added when you install the Remote Installation Service onto your computer system. SIS can reduce the amount of required disk space on a volume when it removes duplicate files.

When the backup program changes the archive bit on an SIS file, FRS detects this activity as a change to the file which activates the replication process.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

This behavior occurs whenever any of the file attributes are changed on files with a "sis" extension in a Dfs share. You may observe additional Windows NT File Replication Service (NTFRS) and Groveler service activity in task manager, on both computers, immediately after making the changes.