The reorientation of hard drives has begun: The first drives to use perpendicular magnetic recording (PMR) technology to pack more data into less space are out. And our tests reveal that they not only boost storage capacity but perform faster as well.
In our tests of the Seagate Momentus 5400.3 and its non-PMR 5400.2 predecessor, the PMR unit showed a modest boost overall, completing its runs in about 7 percent less time; results just for sustained throughput were even more impressive with a 15 to 17 percent gain. The PMR drive's greater areal density has little effect on seek speed, a component of many of our tests, but helped when our tasks focused on sustained throughput with sizable files.
PMR aligns the magnetic markers on a hard-disk surface in a different way to increase areal density so you can store more data on every platter. Existing technology was approaching its areal density limits, and drive manufacturers spent several years working to overcome the problem. The result for you is more and cheaper room for your data--which is no small concern in a world moving to high-definition media.
Inside the Drive
To visualize the difference between today's longitudinal and the new perpendicular recording, picture a drive platter. The bits of data on the disk are represented by magnetized particles with their poles oriented one way or the other. Until now, they have been aligned parallel to the disk surface, like concentric rings formed by tiny dominoes. PMR stands those dominoes on end--also in concentric circles--meaning you can squeeze far more dominoes into a given surface ("How It Works: New Drive Technology" shows the difference).
Toshiba has already shipped 40GB and 80GB, 1.8-inch PMR drives. At press time, only Toshiba's Megabeat MP3 players, sold in Japan, feature them, but they'll be in various consumer electronics devices and laptops soon. The second taste of PMR comes courtesy of Seagate's new 2.5-inch Momentus 5400.3 line, which ranges from 30GB to 160GB. The 160GB model is now the biggest notebook drive available, surpassing the previous 120GB notebook champ. The new drive not only has more storage, it uses less energy and gives off less heat, making for quieter, cooler micro PCs and digital video recorders. One caveat: Many BIOSs do not support drives larger than 137GB natively. Systems with Windows XP SP1 and later, as well as Linux, though, supplant such BIOSs and can recognize the full 160GB.
Seagate predicts that relatively soon PMR technology will deliver at least a four-fold increase in capacity. That means 2-terabyte, 3.5-inch single-platter disks for desktops; 1TB, 2.5-inch disks for laptops; and even 50GB for tiny 1-inch drives in MP3 players in the near future.
Headroom for tomorrow is good, but how much do you gain today? The highest-capacity (500GB), 3.5-inch drives currently on the market have an areal density of 125 gigabits per square inch; the PMR Toshiba models and the Momentus 5400.3 have 133 gbpsi. That's a measurable, if marginal gain, but compared with the average drive's approximately 100 gbpsi, it's a significant improvement.
With a winning combination of more storage and greater speed, the new drives should be a welcome addition to your storage arsenal. And they cost about the same $2 per GB as current drives--you'll find the 160GB Seagate drive kit for $320 (list).
See the next page for a chart of our test results.