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Question: I am not able to span (raid 0) two 4tb hdds with this unit. is it impossible? what am i doing wrong?
Document: My desktop computer has a pair of 1-terabyte drives in a raid-0 configuration. This is becoming a popular setup because the increased read/write speed rivals that of many solid state drives. However, the loss of one of the two drives would be catastrophic because you can't salvage the data on the remaining half by itself.
For under $200 you get a 4 disk USB/eSATA encloser with RAID 0 - 5. Its solid, well made and works.I installed 2x 2Tb Hitachi Ultrastar hds in Raid1. Setup was simple. Install the hds, power on, press mode button till you get the Raid you want, hold the button on the back under the cover for 5 sec and the unit shuts down.
Note that you'll need to format using a GUID partition table for >2.2TB. So that means a Vista, Windows 7 or MAC. On that note, was able to access the array perfectly with a Macbook Pro at the office. Thrilled with this!I have used many external raid arrays that have caused incredible grief. This is not one of them. HIGHLY RECOMMEND!
Thats not really a big deal though, you just power it down manually. I used three Western Digital Caviar Green 3 TB SATA III 64 MB Cache Bare/OEM HDDs in raid 5 configuration. You can also purchase the HDDs on Amazon. They fit well and have given me no problems. All in all for the price it has been an excellent purchase. I have even travel around with it over seas and have had no issues with durability or anything.
This is how I have it hooked up, and it works nicely in Ubuntu Linux without a hitch. Many people will tell you this unit needs a SATA card that supports port replication in order to function. I'm here to tell you they are wrong. *  Because of the hardware RAID support, the OS sees all the drives as a single volume, so no port replication is necessary (if you are using RAID). This is an epic win.
I formatted it as Mac OS Extended (Journaled) and it is showing up and behaving like any other external hdd.I have tested data transfer to it with both USB 2.0 and USB 3.0, and both work as expected. It is able to take advantage of the USB 3.0 speed quite nicely and I am currently transferring 150GB in about 20 mins.
I am currently carrying this between home and office to aggregate all of my files. Today I am ordering another one of these, copying the complete unit, and then will run network sync between home and office. FINALLY I will have my video and pictures properly managed!Setup was easy. Just hold the mode button until the LED flashes, then press to select illuminated raid mode, open back door to hit confirm button -- done! It took about 2 minutes to 'configure' my Raid 5 array.
Bought this to use with my Macbook Pro. it didn't work well..Warnings....1. This is Strictly A Raid device....2. Will not work with only 1 drive....3. This is ERASE any current data on Drives installed4. USB 3.0 didn't detect in my macbook properly...conclusion I had to return device, was useless to me../.
Confirmed working over eSATA with my Synology DS411. I set it up with 4 X 1TB drives, in a stripe configuration (raid 0). I was hoping for more copying speed, but it could be limited by the Synology somehow. Right now I get 60MB/s. Good enough, and a cheap way to add storage, or backup your current data.CONS: The bottom hard drive is a little difficult to connect.
Just a short review. I just wanted to pass on that I installed (4) 3TB Hitachi drives in my enclosure. I tried both 12TB spanning (just to see the big number) but decided on Raid 5 for the parity protection. 9TB in this little box with some parity peace of mind is just great for the price. I have used this both over USB 3.0 and eSATA. Both work equally well. The Hitachi drives run very cool.
Answer: Should not be a problem.  upon powering up, push the raid button to your desired array, then hold the button in the back until it re-boots.