what is the .cdsf file type

I'm currently setting up an avamar backup server to backup a windows filesystem and have CyberSense analyze it. The DD mtree contains a file alled "container.1.cdsf" which seems to have all of the backed up data in it. I was going to look into this file type to better understand it and why cybersense isn't unpacking it but for some reason all results of my searching for this file type returns with "cdfs" file discussions and pages.

What is .cdsf? Is it an error?