Western Digital ok but could do better in terms of software. I do not know the full range, but what timing is difficult: the choice of folders and subfolders penny take forever, so it's just a click to select. Moreover, the newly created folders are not taken into account: it is very risky for a backup disk! ! We must therefore décliquer then click again, and as I have already said, it is very long.
So this is not bad because it is the main function of the disc: a simple and effective sync ... damage.
So, better to secure his rear and do a good old copy and paste on the disc, it's faster and more secure.