Hard-drive builder Western Digital 's (NASDAQ:WDC) Hitachi division is shipping the helium-filled drives we were promised more than a year ago. Helium-infused drives were supposed to cut the total product weight by 20% while reducing mechanical problems and keeping the drive cool at high speeds.

So now that the helium revolution is sitting on store shelves, exactly how well do these drives deliver on their promises? Is this the magic trick that will keep spinning magnetic disks competitive with solid-state drives built around beefy memory chips?

First up, the Hitachi Ultrastar He6 crams seven magnetic platters into the space previously holding only five. The result is a 6-terabyte drive, which is 50% bigger than the largest Ultrastars previously available.

Hitachi's Ultrastar He6 Helium-filled hard drive vs. a standard airlocked version

The helium difference, as explained by Hitachi. Click the image to see a larger version.

The drive case is hermetically sealed to keep the helium from leaking out, and that's another industry first. Hitachi says that it wasn't easy to inject a pure helium atmosphere and then locking the case up tight, all at industrial scale and reasonable pricing (for an enterprise product, you dig -- no $100 drives here). If Seagate Technology (NASDAQ:STX) wants to copy this idea, the company will need to sink serious R&D efforts and dollars into the product.

And the tight seal brings another unexpected bonus feature. These drives can be submerged in water or mineral oil without destroying the internal mechanism. Therefore, these are the first hard drives to offer liquid cooling as an option.

This is huge for data center operators, where cooling racks with hundreds of drives can be a serious and costly headache. A Netflix (NASDAQ:NFLX) spokesman weighed in on Hitachi's press release, celebrating the high-density storage that these helium drives unlock: "As part of our efforts to optimize the delivery ecosystem for Netflix and our Internet Service Provider partners, we strive to build better and better streaming appliances. The high storage density and lower power usage of the Ultrastar He6 hard drives allow us to continue with that goal."

Netflix might not be the first name that comes to mind when you're looking at massive data storage requirements, but then you're forgetting that each Netflix movie is stored in multiple formats. Some of these come in multi-gigabyte file sizes. Do that a few thousand times over, and the numbers run high very quickly. So Hitachi / Western Digital's helium drives come in handy for Netflix with their large capacities, low power usage, and improved cooling options.

Netflix is one business that won't switch to 100% solid-state storage anytime soon. There's still a healthy market for low-cost bulk storage, and Western Digital hopes to snag a larger piece of that opportunity from arch rival Seagate. Western Digital and Seagate currently split the enterprise market right down the middle, each boasting a roughly 50% market share.

Hitachi-branded helium drives just might change that precarious balance.