Just an FYI for those of you thinking about buying Western Digital or almost any other "Green" drive out there - they might not be all they are cracked up to be.
I bought 4x 2 Terabyte drives that I was going to put into a RAID 5 array. I had no idea of the headaches I would soon encounter.
As I found out, the Western Digital Drives actually park the head (move the arm off of the platters) after about 8 seconds of inactivity. Most hard drives produced these days can only do this 300,000 times. When this timer is activated, the disk disappears to the raid card and your entire volume disappears.
Depending on the RAID controller, you may have a mess. Some cards may make you wipe the disk that turned off, and re-instert it to the array - which would then cause it to re-build. My controller just sat at a BIOS screen waiting for me to continue (without the array) or to Destroy (and start over).
Well, I found a program that disabled the internal timer. The documentation indicated that the program would only cause a minor increase in power usage, as the drives not park until they were shut off.
I was copying my data back to my raid when my volume disappeared again. As it turns out, the Green drives are also missing a feature (TLER I think its called). This feature has something to do with skipping bad sectors of the disk before the disk spends a lot of time trying to get a bit of information. Most "Green" drives lack this feature as well.
This stumbling block used to have a solution too - but the newer Western Digital Drives no longer support the method to add this.
I'm in the process of trying Software RAID with a Linux computer, but the early results are discouraging at best.
If you are going to use a Green drive by itself - I'm sure it will work just fine. But the Green drives, at the very least from Western Digital (now owner of Hitachi drives) do not work so well.