Improving Hard Disk Drive Reliability by Studying Bridge Design

On a desktop PC, the hard disk drive (HDD) is the component with the highest failure rate. While our ThinkCentre desktops have among the lowest HDD failure rates in the industry, our engineering team focuses a lot of effort to make these failure rates even lower. So far the payoff has been great. A ThinkCentre you buy today has about 25% of the chance of experiencing a failed HDD drive during its lifecycle than even systems we shipped just three years ago. Recently the team was able to make a small but significant change that will improve reliability even further. To understand what they did, consider a bit of history. One day in 1906, as a group of Russian soldiers went across a bridge in step, the bridge suddenly collapsed. The reason was the soldiers' walking frequency was the same as the bridge's natural frequency, a phenomenon known as sympathetic vibration. From that point forward, a rule was set by the army: When walking across a bridge, soldiers must break step. On November 7th, 1940, the Tacoma Narrows Bridge collapsed suddenly when prevailing winds caused the same phenomenon. Soon after vibration theory became a required course for aspiring engineers. [youtube:] People familiar with the inside of their ThinkCentre PCs will recognize the original HDD caddy design in the diagram below. It first debuted on our ThinkCentre S50 PC and provided both ease of service plus HDD vibration protection. Yet the team found that under certain conditions the design was susceptible to sympathetic vibrations from its environment much like the bridges mentioned above. This could result in premature HDD failure. Using bridge design theory as a model, our engineers were able to come up with a modified design to eliminate the danger with almost zero change in cost. You may claim all desktops are the same and even use the "C" word (commodity), but I offer this as evidence that nothing can be further from the truth. There is still plenty of innovation left to be had in the desktop world.