Just an FYI don't get any of WD's higher capacity multi bay drives. I'm a huge fan of their portable my passport drives, but their NAS drives are incredibly incredibly horrible. The reason is simple, a SATA to USB passthrough is super cheap to build so all that has to happen is you build it right, WD is great at manfacturing. Design and engineering? Not so much.
WD's larger capacity drives and NAS' have internal processors firmware etc etc, and they cut so many corners with them it blows your mind. They have the worst possible hardware, the most underdeveloped half baked firmware, and the whole system is abysmal.
Because the hardware is the slowest in the industry their RAID enclosures and NAS drives will be super flakey. We're talking freezing every 3 hours and transfering at 10 mb/s, when you should be getting upwards of 80 mb/s.
Also the firmware is installed on the drives themselves because WD is too cheap to spring for an external firmware box, so if one drive fails, it doesn't go into degraded RAID mode, it just stops working. WTF? This is the worst possible implementation of RAID 1 I have ever seen.
Anyways like I said if you're looking for anything more than a $5 SATA to USB passthrough, or SATA to thunderbolt passthrough attatched to a drive steer clear of WD. These guys make $200 enclosure with $30 of parts and then sell them as $140-$300 enclosures. (though again the hardware failure rate for WD is lower because they manufacture things well, it's just everything else that's wrong)
I've also looked at all other manufacturers that do NAS RAID drives and they are so incredibly bad. If they don't get the hardware horribly wrong, they get the software or firmware horribly wrong.
LACIE, Promise, everyone
The level of incompetence with NAS RAID drives is somewhere between North Korean missile program, and three stooges.
The only two manufacturers that you can trust farther than you can throw are Synology and QNAP.
Go with anyone else and you will see a CONSISTENT 25%-40% failure rate after 2 years, with super flakey performance.
Synology has a much better 8% failure rate after 2 years, which is 4-5 times lower AND their products perform flawlessly.
QNAP will be a little more buggy, flakey and have a higher 13% failure rate, but their products are still well above and beyond the cheap junk everyone else will sell you.
What I imagine WD's egineering department discussing:
Employee 1: You know this NAS seems to work great but you know the one thing I noticed is that you included a 2.0ghz atom processor with 512mb of ram. Those cost $38, and on a $700 product that's 5% of our profit margin. What can you do with an 800mhz processor and 256mb of ram? That costs $20 less and will improve profit by 3%, and you know that $10 fan you have? That is 1.5% of your profit. Remove that.
Employee 2: That sounds like an insanley bad idea, I'm pretty sure that will make the customers very unhappy. For what, $32 in proft?
Employee 1: Ha ha ha ha customers!
Employee 2: Ha ha ha ha that was a good joke. Also lets get rid of the 1GB of flash memory for the firmware, that costs us 3 bucks.
Employee 1: Good idea. Then we'll market the whole thing as "blazing fast".