The WD 8TB drives are NOT shingled, and are superb drives. I just bought 4 of them (not for UnRAID), and they are VERY nice -- sequential reads well over 250MB/s. They're a bit pricey (~ $320), but well worth it. They're essentially a slower RPM version of the $550 HGST Ultrastar HE8's [ http://www.newegg.com/Product/Product.aspx?Item=N82E16822145969 ], and like the HGST's they're helium-sealed units. They run very cool; look exactly like the HGST units (except, of course, for the WD Red sticker); and perform exceptionally well. I'll definitely use these for my next UnRAID upgrade.
I have all WD RED drives in my system, really happy with them.. I have now gone for the 8tb Seagate because they are slightly faster read/write wise.. Also its good to keep a mix imho