The Pebble and the Avalanche

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Current Revolutions in Business and Technology

by Dr. Moshe Yudkowsky,

author of The Pebble and The Avalanche: How Taking Things Apart Creates Revolutions

 

Fri, 2006-Jan-06, 10:36

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How My Computer Avoided a Disaster

I had a near-disaster on Monday evening: my hard disk hiccuped late in the evening, the kind of glitch that often results in lost data and a frantic search for backup files. But I'd taken advantage of a design based on disaggregation that made the glitch a non-event. In fact, I didn't even notice the hiccup until Thursday evening when I was looking through old mail.

It's pretty easy to think of a "disk" as being a simple object. For example, when I put a CD into my drive, it shows up on Windows as a new disk with its own icon or drive letter. But actually the idea that a physical disk must show up as a single drive on your desktop isn't a hard-and-fast rule, because computer design can be more complex than that. The disk drive that shows up on your desktop can be completely disaggregated from the physical piece of hardware in your computer. What's to stop you from "dividing" — using software — a single physical disk drive in half and having it appear as two separate drives on your desktop? Actually, people do that on Windows computers all the time.

But it's possible to go deeper than that, and that's what saved my computer system. Using a common set of software tools, I configured my system to take advantage of a further disaggregation: a "disk drive" doesn't have to be a single device. A disk drive can be a collection of disks that appears as a single drive to the desktop.

The advantages of a collection of drives, acting as if they were a single device, can be very substantial. In my case, I had two drives acting in tandem, and all data from one is completely replicated on the other. When one of the drives hiccuped, it dropped out of the collection and the other drive kept going — smoothly, invisibly, and without data loss. This kind of setup is called "RAID," by the way, and it's available for any computer system.

So, thank goodness for disaggregation. If someone hadn't thought of separating the idea of "the disk drive that appears on your desktop" from "the actual collection of hardware and whatnot inside your computer," I could have been badly burned. Instead, I've had a smooth and complete recovery.

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