Modern-day hard disk drives (HDDs) hold the interesting juxtaposition of being simultaneously the pinnacle of mass-produced, high-precision mechanical engineering, as well as the most scorned storage technology. Despite being called derogatory names such as ‘spinning rust’, most of these drives manage a lifetime of spinning ultra-smooth magnetic storage platters only nanometers removed from the recording and reading heads whose read arms are twitching around using actuators that manage to position the head precisely above the correct microscopic magnetic trace within milliseconds.
Despite decade after decade of more and more of these magnetic traces being crammed on a single square millimeter of these platters, and the simple read and write heads being replaced every few years by more and more complicated ones, hard drive reliability has gone up. The second quarter report from storage company Backblaze on their HDDs shows that the annual failure rate has gone significantly down compared to last year.
The question is whether this means that HDDs stand to become only more reliable over time, and how upcoming technologies like MAMR and HAMR may affect these metrics over the coming decades.
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“Did I forget something?” It’s that nagging feeling every engineer has when their project is about to be deployed – it may be a product about to be ramped into production, a low volume product, or even a one off like a microsatellite. If you have the time and a few prototypes to spare though, there are ways to alleviate these worries. The key is a test method which has been used in aerospace, military, and other industries for years – Highly Accelerated Life Testing (HALT).
How to HALT
The idea behind HALT testing can be summed up in a couple of sentences:
- Beat your product to death.
- Figure out what broke.
- Fix it, and fix the design.
Sounds barbaric, and in many cases it is. HALT testing is often associated with giant test chambers which are literally designed to torture anything inside them. Liquid nitrogen shock cools the chamber as low as -100°C. The Device Under Test (DUT) can soak at that temperature for hours. Powerful heaters then blast the chamber, causing temperature rises of up to 90°C per minute, topping off at up to 200°C. Pneumatic hammers beat on the chamber table causing vibrations at up to 90 Grms and 10 KHz. Corrosive sprays simulate years of rain and humidity. These chambers are literally hell on earth for any device unlucky enough to be placed inside them. It’s easy to see why this sort of testing is often referred to as “Shake and Bake”.
Continue reading “HALT In The Name Of Testing” →