Recent advances in hard drive technologies suggest that the current perpendicular magnetic recording technology (PMR) may be hitting its limits in the not too distant future. In fact, Seagate agrees that the end is in sight and that the industry will have to transition to a new approach that will allow hard drive manufacturers to continue on the path of massive storage improvements: While PMR may hit just about an aereal storage of 1 Tb/inch2, heat assisted technology will take the industry into the range of 50 Tb/inch2.
Mass storage is surely one of those topics in the IT industry hat is always good for a surprise. I cannot quite remember how often the death of certain technologies, including flash and hard drives, has been predicted. We know that previous predictions that flash would only last until 2008 and that hard drives won’t be scaling past 500 GB in a 3.5” drive turned out to be false.
However, today’s storage technologies still have physical limits, often described as soft physical limits under the assumption that the limit can be pushed out further when needed. That limit is defined by the possible proximity of magnetically charged bits that need to placed in a certain distance from each other so they do not interfere with each other: Data is stored in the magnetic polarization of bits on the cobalt-based alloy disk. A head that hovers above the surface reads and writes data from and to the disk.
The next density limit is approaching. In 2005, the HDD industry moved from linear to perpendicular recording technology, which enabled manufacturers to break through the aereal density barrier of 100 Gb/inch2. The first commercially available PMR HDD, Seagate’s 160 GB Momentus drive, started with 133 Gb/inch2. Back then, it was generally believed that PMR HDDs could hit about 1 Tb/inch2 and it appears that this prediction was accurate as Seagate’s senior vice president or recording media operations, Mark Re, told ConceivablyTech that HDD’s are likely “to top out a little north of 1 Tb/inch2.” Today’s HDD’s are approaching this level quickly, as Seagate’s highest density drive (a 750 GB Momentus notebook drive) is currently at 541 Gb/inch2. Samsung recently announced a drive that exceeds a density of more than 700 Gb/inch2. So, what is next?
Re said that Seagate has a “few more product generations” for PMR left, but he said that the technology will run out of room within “3 to 5 years.” A that time, the industry will have a choice to embrace patterned media or heat-assisted magnetic recording (HAMR) to increase the storage density of hard drives. Re told us that Seagate favors heat assisted recording over patterned media and believes that HAMR will push HDD storage densities into the double digits of terabits. From today’s perspective, HAMR will hit a “soft limit at about 50 Tb/inch2,” he said. While no one can predict the actual capacity of the general hard drive at that time, it seems to be safe to assume that we will be seeing hundreds of terabytes of space on single 3.5” drives. PMR will have lasted for about 8 to 10 years when it runs out of steam and it appears that HAMR, conceivably, will provide at least the same opportunity.
Seagate’s HAMR goes back to Seagate’s acquisition of Quinta in 1998, which has been among the pioneers of heat assisted magnetic recording. Over the past 12 years, Seagate never dropped the ball and kept researching the technology and modified it over time. For example, Re said that Seagate abandoned Quinta’s optical way to integrate optics in the read/write head and will use a traditional read/write head in its HAMR drives instead. There will other subtle changes to those drives, including the metal that is used for HAMR drives, which will be iron-platinum, Re said. He noted that Seagate has built HAMR prototype hard drives, but they aren’t at a level where they could be commercialized yet.
Re is confident that there isn’t a technology that could replace hard drives in the way they provide a compromise of performance, capacity and cost. Flash is often rumored to be catching up with HDD technology, but the executive noted that “there isn’t enough flash memory in the world to replace all hard drives today.” The company is even thinking beyond HAMR already and said that the 50 Tb limit could be pushed out by using a combination of HAMR and patterned media using different materials.
What remains the same with new hard drive generations is their reliability. Today, it is recommended that hard drives should be replaced every 3 to 5 years. Considering the fact that even 1 TB drives can store huge amounts of data and a loss would be catastrophic, data security is a mounting problem. Imagine a 100 TB drive that potentially holds the data of multiple generations of your family would be lost. What would you do? Re said that we should not expect hard drives to improve their reliability in hardware. Instead, Seagate is pushing software innovation and is telling users to back up their data regularly.