Hybrid drive by WD doesn't do well in reviews
FINAL THOUGHTS
The premise behind SSHDs is to combine the responsiveness of solid-state drives with the capacity and low cost per byte of mechanical drives. Unfortunately, it's not a simple task— Seagate has been doing this for a few years yet their drives still pale in comparison to true SSDs. Western Digital is not as experienced in this genre and their latest foray is even more disappointing, with their Blue SSHDs somehow managing to produce poorer overall results than their purely mechanical predecessors. Both the 4TB and 1TB models can boast quick loading times compared to most hard drives, but in all other areas, they lag behind their equivalent capacity WD Red counterparts. Assuming they are simply Green drives with NAND Flash tacked on, this shouldn't be the case, suggesting that WD's hybrid technology has some kinks to iron out.
The 1TB model in particular should be avoided as it is plagued by unusual seek activity. After some of our tests, it would seek for an inordinate amount of time and when it finally stopped, it would continue to seek less frequently in short sporadic busts, delaying headparking and motor spin-down. Not only is this annoying, it decreases its overall idle energy efficiency and will reduce battery time if used in a notebook. Furthermore, its seeks use a relative high amount of power and the drive also produces more vibration than most modern 2.5-inch drives.
The 4TB variant's physical characteristics are excellent, almost indistinguishable form the equivalent WD Red, though it suffers more of a relative performance penalty than its little brother. It may be a good budget choice for a small system that can only fit one drive and needs to be snappy at loading applications above all else, but that's a fairly limited use case. If you're looking for a compromise, it should be noted that for the price of a Blue SSHD 4TB, you can purchase a decent 120GB SSD along with a 3TB WD Red. This route does mean managing an extra drive, however it's tremendously faster solution.
http://www.silentpcreview.com/article1482-page6.html