Way back in 2007, Google published a study on hard drive failure trends. The data revealed that failures typically occur very early in life or after several years of use. The study is a little dated, though, and so is similar research (PDF) conducted by Carnegie Mellon University. Fortunately, we have fresh data from online backup provider Backblaze, which has published failure statistics for 25,000 hard drives bought in the last five years.
According to this data, infant mortality is still a problem. The failure rate for the first three months of operation is higher than for any other quarter until after the three-year mark. Backblaze reports that 5.1% of its drives failed within the first 18 months, followed by only 1.4% for the following 18 months. After three years of use, the failure rate jumps to 11.8%.
Nearly 80% of the drives are still operational after four years. Backblaze doesn't have data points beyond that, but the current trend suggests a median drive life of six years.
Interestingly, the bulk of Backblaze's drives are consumer-grade models rather than enterprise variants with server-specific features and longer warranties. In fact, 8% of the firm's 75PB storage capacity comes from "shucked" drives that began their lives in external enclosures. Backblaze doesn't break down failure rates by drive type, but it promises to detail the differences between consumer- and enterprise-grade models in a future post. Since the company has "standardized" on consumer drives, it seems to be happy with their longevity versus the server-specific alternatives.
Even if enterprise-grade drives fail less frequently, the difference may not be large enough to justify the price premium. Pricing also appears to motivate Backblaze's harvesting of external drives. The firm started shucking portable drives in response to the high prices and limited availability of internal drives that immediately followed 2011's Thailand flooding. A recent blog post suggests the practice continues to this day, perhaps because portable drives are often cheaper to buy than equivalent internal products.
Although Backblaze has pledged to update its reliability statistics every quarter, it doesn't look like we'll get a manufacturer breakdown. I'd be very curious to see whether any makes or models are failing more often than others.