Hidden files being written to attached USB drives

I have a 4T mycloud, with two attached USB 8T drives .
the 8T drives are full of lots of avi, mpeg etc etc.
I notice that the free space of the 8T drives is going down and down

I see no new files when using IE to look at the directory structure and I see
no new files when I SSH into the mycloud and look using ls -altr etc etc

I look at TOP and see no big CPU processes, and as far as I can tell,
I am not running sync or streaming service .

any ideas about how to discover what is happening?

many thanks for any hints

[quote=“BOB_BOLDI, post:1, topic:193589, full:true”]
I see no new files when using IE to look at the directory structure…[/quote]
By “IE”, do you mean Internet Explorer? Where you accessing the WD My Cloud Dashboard with Internet Explorer? Or the Mycloud.com with Internet Explorer?

What about removing the two USB drives and attaching them to a computer and using Windows File Explorer (or if using a Mac, Finder) to view the USB drives properties and files?

Are you running a My Cloud Safepont / Backup to either or both of the USB drives? Have you made any changes to the My Cloud firmware using SSH? Are you running any other WD software like Smartware or WD Sync that is backing up or syncing to the My Cloud?

Dear Bennor - thanks for the interest -

I access the mycloud using a windows machine with the mycloud usb drives mapped to drive letters.
I then use windows-explorer to navigate the directory structure. ( set to show hidden files )

I have not modified the software of mycloud at all, and I have not / am not using any backup software on the system.

I have removed the 8T usb drives, and attached them to a windows PC.
they show being completely full ( 4k free ).
started looking for new files -
any idea of what type of files they might be IF I HAD SYNC on somehow without my knowing it?

If you have connected the USB drives to a PC and used Windows File Explorer to view them, have you determined the files that are now taking up the space or that shouldn’t be there? There are various 3rd party programs/software one can use to show which files are taking up the most storage space on a hard drive.

Generally WD Sync creates a subfolder that starts with a period (example: .wdsync) and will fill it with either failed sync files or version backup files. One may have to enable hidden files/folders in Windows File Explorer.