Scott Lowe explores a new frontier in drive capacity — helium.
Sometimes, physics can be a real pain in the neck. Nowhere is that more true than when it comes to the ever growing demand for newer and larger hard drives. What amazes me is that each time it appears as if the industry has hit a road block when it comes to increasing drive capacity, some really smart people get together and do some amazing things. A few years ago, as storage density began to approach levels that would result in hitting limits as a result of the superparamagnetic effect, the industry just flipped... to perpendicular storage. This staved off the coming magnetic dark ages that would have stopped capacity increases in their tracks.
Today's physics challenge isn't magnetism... its air. Yes, air. If you were to open up a modern hard drive, you would find that it actually has holes in it. As the platters of a hard drive spin, air is also pulled into and pushed out of the drive. The drive's read and write heads ride an extremely thin cushion of air to avoid sliding across and damaging the hard drive platters. Through this tiny air cushion, the drives read and write heads do their duty, reading data from and writing data to the hard drive. However, like a jet engine pulling air into and blowing it out of the engines, this constant flow of air creates turbulence that can push the read and writes heads off their intended track. This results in inefficiencies and makes it more difficult for manufacturers to create denser drives. This phenomenon is known as track misregistration.
Further, the air gap places some limits on how many platters manufacturers are able to place into hard drives. Hitachi Global Storage Technologies (HGST), an arm of Western Digital, currently uses five platters in hard drives and, with traditional technologies, is releasing a hard drive that boasts 4 TB of capacity... a single unit. That's pretty impressive.
But, it's not enough for the ever-growing demands of exploding cloud providers that need cheap and reliable storage to meet customer demand. To that end, HGST has turned to helium. Rather than forcing air through the drive, helium filled drives will be hermetically sealed to keep the helium in and the bad stuff out. Helium is lighter than air and, as a result, will provide less drag on the platters than air does. Further, because the drives will be fully sealed, they will operate at slightly lower temperatures and in harsher conditions.
With the introduction of helium, HGST indicates that they will be able to add two more platters to helium-based drives. Assuming that the data density stays the same - although HGST indicates that storage density may also increase - that's a 40% increase in platters, meaning that we might see drives approaching 6TB in size next year.
Further, with less drag on the platters comes the ability to operate drives with a little less power. While the power savings from a single drive may not be that much, as you scale this to cloud-provider size, that power savings could be significant. Further, given that HGST estimates that drives may be able to run cooler, it might be possible to adjust data center temperatures up just a little bit, further improving power savings.
What do you think if this latest trend in increasing hard drive density? Is there something to it or is HGST just full of hot air?