I have a 750Gb disk in one slot of my NAS that has less than 500Gb of data on it but it is almost out of space (<30Gb free).
If I right click on a folder and select properties I get a page in one case that says 'Size 5.65Gb, size on disk 16.5Gb'. All folders are similar and in one case size on disk is 88Gb greater than size. However if I look at the same data for the source folders on my PC it says in the case of the first folder 'size 5.65Gb, size on disk 5.67Gb' so it appears that the NAS is wasting huge amounts of disc space.
What can I do to avoid this problem? It seems wrong that a 750Gb disk is out of space with less than 500Gb data.