This hard drive has been really convenient to me. It holds a total of 4 hard drives 2 built for fast data transfer while the other two hard drives back up all you information so that if one fails you still have all your data saved on the other hard drive. The cons to this product is when you turn it on and its all set up you will hear a buzzing noise in your speaker. Its low but still unwanted. Also, The power button is on the front and the button to switch from one pair of hard drives to the other is on the back. This is not convenient if you want to place it in a rack. Overall I am Happy though.