It is a continuation of the previous post of mine. I just set up reformatting WD MyBook (500Gb) to NTFS and there was an option I've never used although been aware of it:

Enable File Compression. I checked it without realizing the consequences. What are the possible consequences? I kind of doubt that I will actually need it for my data. It is mostly number crunching but I most likely start storing more still photos from now on.

My major usage (the way I envisage it) is to use it for system backup and restore.

Could you give me a crach course on this narrow subject?

Thanks.