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The first hard drive roared to life in 1956. Designed and built by IBM, it was as big as a refrigerator and loaded with 50 two-foot aluminum platters, each coated with an iron oxide paint that served as the magnetic storage medium. The 1200rpm drive - dubbed the 305 RAMAC - was accessed by a pneumatic read/write mechanism and provided a whopping 5MB of storage space.
Flash to 2002, and the more things change, the more they stay the same. Millions of transistors have been added - the device itself has shrunk as dramatically as the hero of a grade-B science fiction movie - but the basic mechanics remain the same. Look ahead three to five years, and perhaps even more surprising is that no immediate successor for this amazingly durable technology seems close to realization. "I spent my early career looking for replacements for magnetic recording, and I think 10 years ago those replacements were closer than they are today," says Vic Jipson, an executive vice president for Maxtor, Milpitas, CA.
"Call me skeptical, but I've been hearing about [hard drive] replacement technologies for a long time and they haven't happened," says Mark Geenen, president of the research firm TrendFocus, Los Altos, CA. "I just don't see there being any significant competing technology in PCs and servers for a long time."
What accounts for this amazing longevity? Continuous improvement, mainly. Most impressive has been the increase in areal density - the number of bits per square inch of storage space - which rose by 60% per year from 1991 through 1996 and a stunning 100% per year from 1997 to 2002. Hard drive performance increases have been less spectacular, but new caching techniques and plummeting costs per gigabyte have neutralized competition from ultra-fast solid state disks, which continue to cost hundreds of times more than conventional drives.
Peer far enough down the road, of course, and the outlines of the hard drive's successors begin to emerge, including new storage schemes involving lasers or plastic disks. But over the next three to five years, the hard drive almost certainly will stand alone as the workhorse of computer storage. The general consensus is starting next year, areal density increases will slip back to 60% year over year, but that will still result in terabyte drives by 2005. For mainstream servers and desktops, however, the most important hard drive improvements will derive from smarter interfaces and new breed of high-performance 2 1/2-inch drives.
Drowning in gigabytes
Server and desktop hard drives have different requirements, but their immediate futures hinge on similar market forces. On the desktop, hard drives' capacity have already far outstripped necessity, according to TrendFocus' Geenen. "The disk drive industry has for years been deluding itself that, oh God, people need 40, 60, 80, 100GB of storage," he says. "That's beyond the lunatic fringe. I don't know what subspecies of the race would demand 120GB on their desktop."
As most storage professionals know, there's even less motivation to buy large-capacity drives for servers. The higher the areal density, the more data a platter can hold - and the more a platter's read/write head must skip around to access that data. Today, wide interfaces, low CPU utilization and high rotational speeds have largely made transfer rates a moot point - the average ATA hard drive can stream half a dozen MPEG2 videos simultaneously without choking. Instead, the number I/Os per second (I/Ops) is the main constraint on server hard drive performance - which drops as the number of gigabytes per read/write head increases.
That makes I/Ops - not capacity - the real frontier for future server drives. Currie Munce, advanced hard disk drive technology director for IBM, says that fact is reflected in a pattern prevalent today: "People willing to trade dollars per gigabyte in exchange for I/Ops per gigabyte," so they connect smaller-capacity drives to RAID controllers that stripe data for fast access.
| Road map for hard drive technology |
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The road to higher I/Ops rates is paved with fast-spinning drives working in parallel. Instead of areal density barriers, the main obstacles are rotational speed, physical space, cooling concerns and power consumption. As an example, Munce recounts the anecdote about a server farm once planned for the Seattle suburbs, which would have sucked 1/8 the watts of Seattle's total capacity. Watts per gigabyte, he says, is an underrated metric.
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