Hard drives haven't really undergone any truly revolutionary changes in decades, possibly since the move to integrated drive electronics (IDE). Sure, they've received upgrades to areal density so that current devices can hold far more than even their close ancestors of a few years ago and gobs more than the 10MB of the top of the line drives from the 1980s. We've also seen them switch from parallel ATA (PATA) to serial ATA (SATA) and watched as the industry endowed them with faster data access speeds, longer life spans, and enhanced reliability. Still, these have been more an evolution than revolution.

The one upgrade that has been revolutionary is the move from a horizontal to a perpendicular recording scheme. I can hear the head scratching in the back rows

Picture a dinner plate covered in a thin layer of lobster sauce. You've eaten the shrimp already so all that's left is the white rice sitting the sauce and, by some cosmic intervention, all of the grains are lying flat (horizontally!) on the plate, end to end, a spiral pattern that stretches from the outer rim of the plate to its center. (Some intervention, huh?)

The plate is analogous to a hard drive's substrate, the lobster sauce to the slurry that's used on that substrate to hold the ferric particles (the rice, in this case) in place. Hard disk manufacturers spin the substrate to get the particles to align as noted. We relied on cosmic intervention to keep you from being ejected from the restaurant.

You can employ a variety of techniques to pack more and more rice onto the dish in that manner but, at some point, the length of the rice (or the ferric particle) becomes the real limiting factor. Bottom line: you can only fit ten 1-micron wide particles in a 10-micron space.

But what if you could get the cosmos to intervene once again and, this time, when it's packing your rice on your lobster sauce-coated plate, it stands up the grains (perpendicularly!) instead? The particles are much thinner than they are wide so many more of them could fit in the same space! Effectively, this re-alignment would increase your plate's areal density. (Proven, of course, by the fact that your waiter would have to bring you more rice to fill the same space.)

That's the crux of it. Naturally there are technical details, urban legends, and nuances of conduct that really define the technology. Feel free to do the research. This isn't the time or the place for that. We're gathered here today (after polishing off a reasonable meal of shrimp with lobster sauce) to determine if there's any speed difference between the two different technologies, horizontal and perpendicular. That's why they pay me the big roll of quarters.

The test system we'll use began life with an ASUS P5WD2-E Premium motherboard stuffed with a Pentium 955 Extreme Edition processor (cranked up to 4GHz) and 1GB of memory. The motherboard supports RAID and that's the connection point for the hard drives.

Both pairs are from Seagate. The first was two 300GB ST3300622AS horizontal drives. The second pair was composed of two 320GB ST3320620AS perpendicular drives. All four are SATA 3.0GB with 16MB of cache. The operating system for the computer is Windows XP Media Center Edition. The test used is called HD Tach version 3.0.1.0 from Simpli Software. No adult beverages were consumed during the tests.