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The legend of the laptop and the Savvio 15K-rpm drive

Since the introduction of the first Seagate Savvio 2.5-inch enterprise drives back in 2004, I’ve corresponded with many people who would tell me, “If only it was a SATA drive, I could install one of those inside my laptop and get blazing performance along with all that enterprise reliability.”

The SAS interface seemed to be the only blocking element that would otherwise allow the Savvio to run in a laptop. Fast-forward to today and now we have the Constellation family of enterprise drives in a 2.5-inch form factor as well. And these drives are available in SAS and SATA, and offer users up to 1TB of capacity.

Although it has a 2.5-inch form factor, the Constellation.2 is not designed for laptops

And now that there is a SATA version of the Constellation.2, there’s been a lot of interest and some confusion over whether someone can use the drive in a laptop. Let’s give out the quick answer first and tell you that the SATA version of the Constellation will NOT work inside a laptop. End of story. Now, for those that want to know more about the details of why, read on.

It’s all about the environment, so let’s look at the typical laptop environment first. A laptop drive like the Seagate Momentus is optimized to work in a tight space with limited airflow. But the drive also needs to use as little power as possible so that it won’t drain a laptop’s battery too quickly. Fortunately, when you design a drive to use less power, the added benefit is that the drive itself will generate less heat. Less heat means less cooling is required. So in the end, a drive that draws less power and requires less cooling means that it can work well in those cramped laptop quarters. Now there are other requirements for laptop computers that HDDs need, like lower noise acoustics and vibration, but we’ll save that for another discussion.

On the other hand, an enterprise-class drive has a different set of requirements by design. Overall power consumption is certainly still important, but data center servers don’t run on batteries, so it’s not the primary goal. For the enterprise, drive performance, having higher capacities and maintaining the utmost drive reliability are the most important design elements.

With that in mind, when Seagate engineers designed drives for the then new enterprise 2.5-inch form factor years ago, the drives themselves were created with a larger height (also sometimes referred to as  z-height which relates to an x,y,z chart or diagram). This continues to this day as a Constellation.2 enterprise drive has a height of 15 mm. A Momentus XT drive in comparison is slimmer, with a height of 9.5 mm. The added height of the Constellation.2 is also one of the reasons why it’s able to offer an increased 1TB of capacity.

Seagate's Momentus XT merges SSD performance with HDD high capacity and lower cost for mobile computing

Then there’s the issue of power. To make a laptop operate on the least amount of power possible, a laptop drive will operate from the SATA connector’s 5 volt (5v) line. All other SATA drives require power from a SATA connection’s 5v and 12v lines. So in other words, even if you were to physically make a Constellation-series enterprise drive fit into a laptop, the laptop’s SATA connector would only supply the power for 5v and not the additional 12v required.

Related to the power supply itself is the power consumption as we discussed earlier. If we examine specs of a Momentus XT drive vs. a Constellation.2, we’d see that the Momentus XT draws an average of .8W at idle and about 1.5W seeking, whereas the Constellation.2 1TB SATA will draw about 3.3W at idle and 5.2W when typically seeking. This means that even if it was possible for a Constellation to be used in a laptop and run off the battery, it would drain rather quickly. The Constellation also wouldn’t receive adequate cooling inside a laptop either since it draws more power. Again, this is all about designing the drive for the environment for which it will be used.

The newest storage magic for today’s mobile computing environments is the solid state hybrid drive (like Seagate’s Momentus XT) where the desired attributes of high-performance and capacity have come together in one design. Through satisfying the high-performance demands by using onboard SLC NAND flash along with the higher capacities offered with traditional HDDs, the Momentus XT allows mobile computing users to have their cake and eat it too…and the Savvio and Constellation enterprise 2.5-inch drives can stay inside the world’s data centers.


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