Hard Drive Reliability Ratings

Many of you wrote in to share your thoughts on extending the life of your hard drive in response to my post on whether to close the laptop's cover (a/k/a stop the drive from spinning). Your comments sent me back to check out how hard drives are rated for reliability to see if I could add anything to the discussion based on benchmarks. I'm not sure that the benchmarks add anything meaningful to the conversation.

Here's an example. I replaced one of my failed laptop drives with a Toshiba MK8025GAS. According to Toshiba, this drive has the following reliability characteristics:

• MTBF (Mean Time Between Failure): 300,000 hours
• Power-On Hours: 2,800 hours
• Product Life: 5 years or 20,000 Power-On hours

Is this sort of chart helpful? Well, it's hard to say, since each number offers a wildly different way of looking at the life of the drive. The chart has three separate specifications, ranging from 2,800 hours (116 days, or about four months), to 20,000 hours (about 2.3 years), to 300,000 hours (about 34 years).

If you use the 34-year spec as your guide, then turning off your not-in-use laptop seems like a waste of energy. If you believe the four-month spec, then you're probably going to be too paranoid to ever turn your laptop on. (Grin.) If you believe the 2.3-year spec on product life, then turning off a not-in-use drive makes sense. It's great that Toshiba's site lists these ratings, because many others don't, but they sure don't help clear up the debate.

Mean Time Between Failure is probably the best-defined term for looking at hard drive reliability. It refers to the average amount of time that will pass between random failures on a drive of a given type. But according to Storage Review it is only meant to be used in conjunction with a Service Life measurement.

Power-On should provide a more reasonable measure of the hours your laptop can spend in a power-on state, but it's a somewhat inscrutable definition, and each manufacturer interprets it differently. Storage Review talks about other measurements like power dissipation that seem more helpful to me. As for the final specification, Product Life, I've never understood how a company can predict the product life of a product that hasn't even been to market yet, as they do with all new hard drives.

All this is a way of saying these ratings and scores represent data points, but they are confusing and probably less helpful than you might think. Maybe all of the benchmark mavens out there can chime in, but I'd love to see one REAL number that would let us compare the various hard drives and rank their reliability and longevity in a more sensible way.

Next we'll look at something that's probably more important than the benchmark ratings, and that's how to keep your machine operating so that environmental factors don't kill your hard drive. I'll share your comments so we all get smart.