I ran across this a while back:

http://www.electronista.com/articles/08/12/17/toshiba.512gb.ssd/

…in which the author breathlessly proclaims: “Longevity is also a focus with about one million hours (114 years) between failures thanks to reduced wear on potentially short-lived memory cells.”

Wrong.

I often get asked about MTBF (Mean Time Between Failure) and it’s amazing how many “industry people” don’t understand it.

And for those who have already figured out that their 1.5M MTBF drives don’t last 171 years, but are not sure what that MTBF thing is… here’s a vastly oversimplified quickie:

Why your hard drive doesn’t last 150 years.

(There are about 8700 hours in a year, but to make this example simple, let’s call it 10,000.)

Here’s how MTBF works: it’s an aggregate of many units based on expected life of a single unit.

Let’s say you have a hard drive that is warranted to last 3 years, or 30,000 hours.

You put it in a server, and behold, it lasts 3 years. You take it out and put in a new one, and that also lasts 3 years. So you replace it with a new one, and that too…. well, you get it.

Let’s say you keep doing that and finally, on the 50th unit, only two years into it’s life, it breaks.

You now have 3 years or 30,000 hours per unit, times 50 units = 1,500,000.

And that’s your MTBF.

So anyone who says “Wow! MTBF of 1.5 million hours! that mean this thing will last (1.5M / 10000) 150 years!” -clearly- doesn’t know what they’re talking about.

(I have grossly oversimplified the description of MTBF calculation in order to make the general point that it is NOT life-expectancy. MTBF is more complex than my example, including “infant mortality” and “wear out” phases; “theoretical” vs “operational” MTBF and so on, but the gist of what’s here is correct.)