In Brief: Hard Drive Reliability and Failure Testing

By Norman Chan

The results of Backblaze's five-year study.

Online backup service Backblaze (one of The Wirecutter's two recommended cloud backup services) just posted an interesting report on the annual failure rates of the 27,000 consumer hard drives spinning in their data centers. It's a follow-up on the company's earlier post about the median lifespan of a consumer drive based on their five years of operation. In buying drives for its data centers, Backblaze says that it looks to both cost-effectiveness and reliability, choosing drive models from three primary manufacturers: Western Digital, Seagate, and Hitachi. Based on this chart, it would seem that Seagate drives suffer from the worst annual failure rates--with one 1.5TB model (ST31500341AS) failing at a rate of 25.4% over an average of 4 years.

But it's worth Backblaze's blog post in detail before jumping to conclusions. The way they select and use their drives is appropriate for a data center environment, which isn't how most consumers stress their storage. For example, the popular Western Digital Green drives aren't suitable for Backblaze, because of the way they rapidly spin up and down to conserve energy use. Google issued a similar report in 2007 based on its testing of drives (its data centers also use drives from a variety of manufactures), and while it didn't call out brand names, its researchers concluded that drive models and "vintages" were just as important a factor to reliability as manufacturer. Arstechnica has more analysis on what Backblaze's results mean in terms of a manufacturers' mean-time-between-failures (MTBF) claims, a spec that Seagate no longer relies on.