Backblaze recently concluded that its use of consumer-grade hard drives makes economic sense. The online backup company has now gone a step further, determining that enterprise-grade drives aren't even more reliable -- at least in its circumstances.
Enterprise drives are designed to work amid the vibrations common in fan-cooled machines bolted to metal racks and are tested to work for many, many hours. But in a study published Wednesday, Backblaze decided they don't actually offer better reliability than their consumer-grade counterparts.
"Are enterprise drives worth the cost? From a pure reliability perspective, the data we have says the answer is clear: No," Backblaze distinguished engineer Brian Beach said Wednesday. Longer warranties can help defray costs, but "that's a benefit only if the higher price you pay for the longer warranty is less that what you expect to spend on replacing the drive. If you're OK with buying the replacements yourself after the warranty is up, then buy the cheaper consumer drives."
Backblaze measured reliability in failure per drive-year, where a drive-year is one year of operation of drive -- for example a single drive running for a year or four drives running for a quarter year. It compared data for drives for a period starting in mid-April.
There were 613 failures in 14,719 drive-years for the consumer drives and 17 failures in 368 drive-years for enterprise drives. That's a 4.2 percent and 4.6 percent annual failure rate, respectively.
There's some wiggle room in the study. For example, the enterprise drives were used in the company's business servers, handling things like sales transactions and not the core data backup work. It's not clear whether there are differences in drive age between the two categories, too. And Backblaze might build better storage units than average; for example, its latest-generation storage pod design has more vibration protection.
The drive-age issue, though, actually weighs against them, Beach told CNET.
"The enterprise drives are overall younger than the consumer drives. As an experiment, I filtered out the older consumer drives so the ages of the populations were similar," he said. "The result was that the consumer drives looked even better."
Enterprise drives can cost significantly more. For example, a consumer-grade 4TB Western Digital 7,200rpm SATA III drive with a 64MB cache and five-year warranty costs about $220 on Amazon right now. An enterprise version with comparable specs costs $279 for a model designed for large-scale storage environments -- and $315 for a model designed with a higher level of durability.
Updated at 6:32 a.m. PT to note that the relative youth of Backblaze's enterprise drives weighs against them in Backblaze's reliability study.