It'll definitely wipe and reformat the first drive you put in, as it needs to put some OS stuff on it. As for others drives, well... I've been told that the only thing you can put in there without the DiskStation wiping it is a drive from another DiskStation. This is annoying, and I'm still running my main storage drive off USB because of this (because I refuse to buy a 2TB drive for £150).
That's a bummer. I do have a second copy of everything from that drive so I won't lose anything, but it'll mean that I'll have to wipe it then put a 1tb of data back on it, but suppose thats' better than have to copy back 2tb or more.
Cheers.
