PC storage trends: Hard drives hard to kill

When it comes to storage, hard drives have more and more competition — but they are likely to stay around for the next few years, sources agree. But while it has competition, hard drive technology has not been rapidly changing. While the power of computer chips have been doubling every other year for decades, in conformance with Moore’s Law, no such force is at work with hard drives, notes John Rydning, research director at industry analyst firm IDC. Performance has been improved mostly by increasing the areal density of the platters (i.e., the amount of bits that can be crammed into a square inch) but density improvements are coming slower and slower, he says. Two types of hard drives are currently used in office computers: 2.5-inch and 3.5-inch form-factors (referring to the diameter of the spinning platters), explains Rydning. The 2.5-inch units are typically used in portable machines while the 3.5-inch units are typically used in desktop machines. Currently the highest capacity available in the 3.5-inch form-factor is about four terabytes, while the highest capacity available in the 2.5-inch form-factor is about 1.5 terabytes, he notes. (A terabyte is a thousand gigabytes, or one trillion bytes.) Another way to increase density has been to add platters. Rydning explains that there are ongoing efforts to make the platters thinner, not only to add more platters to each drive but so that hard drives can fit into thin laptops. Currently, mobile machines may have as many as two platters, while desktop machines usually have three but may have as many as five. The I/O speed of hard drives is determined by their rotational speeds, notes David Hill, principal at an analyst firm called the Mesabi Group. For about the last decade the vendors have been offering the same three speeds: 7,200, 10,000, and 15,000 RPM. Mechanical limitations make it unlikely that they can rotate much faster, he says. In terms of technology, the main competition for hard drives is solid state drives, using NAND flash memory devices. Such memories are non-volatile, meaning their contents survive after the power is turned off (unlike RAM), but they are faster than hard drives and have no moving parts. However, solid state memory costs about a dollar per gigabyte while hard drive storage costs about 10 cents per gigabyte, Rydning notes. But vendors are spanning the difference by offering hybrids — hard drives with solid state caches — which store the most frequently used files and accelerate access. The caching algorithm is very important, he says. If you use flash up front that will save you money on software costs, adds Hill. “You’ll be able to use storage more efficiently and break even on flash.” Flash memory is the only real storage option for tablets, as they lack hard drives. (Cell phones and memory sticks also rely on it, of course.) Meanwhile, the users have begun to compare the speed of their office machines to that of their flash-based tablets, and the office machines come off unfavorably, Rydning notes. But even with solid state drives, desktop units will need retooled operating systems and applications before they can be as fast as tablets. In the future, Rydning expects that the personal computer storage market will fragment. At the low end we can expect to see systems using conventional hard drives that may have large capacities but may not be particularly fast. At the high end we can expect to see solid state drives delivering maximum speed for those who are willing to pay for it. Mid-range systems will use hybrid technologies to selectively boost speed, he predicts. “If you need terabytes of memory you won’t use flash storage,” Hill says. “But if you need 200 gigabytes you will.” Hill also notes that users are increasingly interconnecting with web-based archival storage, so that their needs for local storage are no longer open-ended. Also, today’s hard drives with capacities of hundreds of gigabytes are perfectly adequate for many users. Says Hill: “I used to run out of space, but not anymore. There could be a point of diminishing returns concerning the storage needs of the desktop.” The growing use of VDI (virtual desktop integration) in enterprises may also cut storage demand, as one copy of the operating system is stored centrally, rather than on each desktop, facilitating upgrades and enhancing security, he adds.