I had this problem a few weeks ago where my C: drive would fill up over night. When I came to work in the morning my drive would be full, after reboot I'd about 200GB free. I tried cleaning up with disk clean but that didn't free enough up, then I looked at winDirStat and it only show 300GB of space being used. After getting super confused I found out how to display the "unknown" file type and found that was filling all of the free space. After a lot of duck(and google)-fu I found about the storage sense and cleared up the storage issue.
Today I get a notice from backblaze that my disk space is low, and sure enough these unknown files are back, but this time StorageSense isn't removing them. so I'm sitting on 101GB of spacing being used by non-file objects.
Sorry for the novel, TLDR:
- Drive was full
- Windirstat(as admin) shows 200 gigs not used by files, taken up by unknown
- Cleaned unknown space hogs with StorageSense, stopped being and issue
- Wait couple weeks
- free space is fill again with unknown data
- StorageSense isn't cleaning