Backup is eating all my free space on SOURCE volume?!?

[kikensei]

Hi,

We've been having some stability issues w/ our backup program (BE), so I decided to temporarily use a client desktop PC w/ a portable USB hard drive to backup our user home drives.

We have 1-200GB of data, CAD files, images, docs, etc. When I use a backup program to go over our gigabit network from the client PC to our mapped server drive, the backup starts using all the free space on the source volume!

All settings are correct, and the backup software is copying files from our server to the portable USB drive attached to the client PC. However, slowly but surely, our Home volume on NW 6.5 (SP4) also starts losing all it's free space.

Now I'm afraid to run backups because I don't want to lose all space on the volume. We had 73 GB of free space yesterday when I launched the backup, and only 23GB available when I just checked this morning. When I do searches on the volume for recently modified files, I'm not seeing any detritus from the backup software (I've used Syncback Pro and HandyBackup). Any ideas on what could be using up the free space and how I might be able to reclaim it?