The second generation of “helium” HGST drives now has reached a limit on capacity due to using standard perpendicular recording. Besides, they are lighter, use less power and heat less. It remains only to measure the performance.
By the time HGST in 2013 released a series of drives He6 with a record at the time of 6 TB, the makers of hard drives have long fueled interest in the project of HDD as a sealed vessel filled with light gas – helium. However, so far only HGST considered it appropriate and was able to start mass production of these devices based on the technology HelioSeal.
But first, a few words about where in general the idea of “helium” HDD. Contrary to popular belief, the body of the standard the hard drive is not sealed. Moreover, a particular gas density is required for work, as reading and writing heads are floating above the surface of the plate supported by a special “wing” (slider) at a height of 5-10 nm. At the same time, with the speed at which the HDD spindle rotates, air creates a sufficiently large resistance heating plates and consuming the power of the motor. Furthermore, turbulence rocks plate, because of which they have to be thick enough. For these reasons, the hard drive of standard thickness of 26 mm typically contains no more than five plates, and attempts to accommodate more of them are fraught with difficulties.
All these problems are retreating, if fill space within HDD with the gas less dense than air. Helium (1/7 air density) has been selected through a combination of safety and price of manufacturing of a sealed body, although in itself it is pretty expensive stuff. The nearest alternative – hydrogen – was rejected due to the fact that it is highly flammable and more chemically active. Thin air is not suitable too, because in that case it would be difficult to maintain the integrity due to the pressure difference inside and outside the body.
Hard Drives of series Ultrastar He8 reached the volume of 8TB using seven plates in the body due to the higher recording density compared to the previous generation. Net capacity of the plate is 1,142 terabytes. In conjunction with the rotation speed of 7200 rev/min line speed of reading/writing reached is close to those of advanced server drives with form factor 2.5-inch. However, the second model in the series with a full capacity of 6 terabyte is probably a little different in recording density, because it has a bit worse characteristics: 195 against 205 MB/s at linear reading/writing.
However, the advantages of the linear speed of He8 are not limited by the capacity and high performance. Peak power consumption (7.4 W) of the disc is lower than that of “air” series drives Ultrastar 7K6000 (9,1 W). The weight is less – 650 against 715 g. Indicators of fault tolerance (2.5 million hours MTBF) better than any other known enterprise-class hard disk drives (2 million hours).
Discs are supplied in a configuration with the SATA interface of 6 Gbit/s or SAS 12 Gbit/s. There are options with emulation of 512-bit sectors or native access to 4K sectors.
The main consumer of such HDDs is still the organizations, but they will be also available in retail. With prices the situation is as follows. In the US, Ultrastar He8 of 6 terabytes is sold for almost the same money as the “air” Ultrastar 7K6000.
Body cover of Ultrastar He8 is attached by laser welding to keep the gas inside. Actually, sealing technology HelioSeal employs automated equipment for laser welding – this is the know-how of HGST that has led to the mass production of “helium” drives. In theory, the drive allows for even immersion in the cooling liquid (of course, electrically neutral, because the controller board is still open).
Mounting holes on the bottom of the body are placed differently than in most other HDD: central row of holes is transferred to the side opposite from the connectors. Therefore He8 not does not combine with baskets in some servers and NAS.