The Seagate 4TB hard drive exists. The engineers have their hands on them and are working to certify them for use in our products.  We can’t ship them yet, but keep an eye out here.  We’ll make an announcement when they’re available to purchase.  Keep in mind 2TB are not supported by Windows XP or older 32‐bit operating systems, which limit maximum volume size to 2TB. Solutions greater than 2TB are compatible with XP 64 bit, Mac OS X, Windows Vista, Windows 2003 SP1, or other 64‐bit operating systems by formatting the disks GPT.