Laying the foundation for a worry-free data center, Western Digital delivers capacity to conquer the data explosion - Ultrastar DC HC520, previously known as Ultrastar He12 and part of the HC500 series of helium-filled hard drives. The stable internal environment created by fourth-generation HelioSeal technology enables a 8-disk design, increasing the capacity by 20% when compared to the 7-disk design of the prior generation, Ultrastar DC HC510.