Online backup provider Backblaze
has begun to evaluate drive failure rates with commercial-grade drives. The company maintains 25,000 drives spinning 24 hours a day -- roughly one quarter of Facebook's capacity -- and has noted
that 78 percent of the drives they have purchased have lasted longer than four years.
According to a blog post noting the study, "Backblaze has standardized on 'consumer-grade' hard drives. While hard drive companies say these drives are not designed to work in RAID arrays or the 24×7 workload of a data center environment, Backblaze uses software redundancy to protect data." Future work will be done by Backblaze to see if enterprise-class drives are worth the added expense.
The company notes that for the first 18 months of use, one in 20 drives fails per annum. For a period thereafter, the rate falls somewhat, then starts to rise at the three-year mark.
While the report is unable to say what the lifespan of the average drive is, the company believes that "the number that we will be able to compute soon, and the one that is more likely to be useful, is the median lifespan of a new drive. In other words, at what age have half of the drives failed? We are starting to get an idea what the answer will be."
The company has evidence pointing to lifespan of drives. For the first 1.5 years of a drive's use, the company has seen drives fail at 5.1 percent per year. For the next 1.5 years, drives fail less often at about 1.4 percent per year. After three years, failure rates skyrocket to 11.8 percent per year. So, 80 percent of drives in Backblaze's experience, will last four years, given proper thermal management and no other outside problems interfering, such as power fluctuations or mechanical shock.
The company has mathematically extrapolated its graph, and believes that the median lifespan of a drive running 24 hours a day is six years.