My Book seems to have ghost space

WD External and Portable SSD External SSD for Windows
1

I have a My Book 25EE, 3 TB. Its companion is a Toshiba 3 TB, and they are used such as to have the identical directories. Using the freeware WinDirStat, they were showing the same size, but the My Book had about 250 GB less of available space than the Toshiba :rage:, so I did a quick format of the My Book (which then showed 2.72 GB out of 2.72 GB available - and then copied a directory of about 200 GB (about 280K files), and sure enough, got about 250 GB less available space than there should be. :rage: :rage:

I used the WD Tools, and it passed with no problems. I don’t know what to do. Should I do a deep format?

3

So why does the Toshiba external drive not have this problem? Is Western Digital just an inferior manufacturer?