BackBlaze 250 Petabyte HDD Reliability Report Shows 8TB Hard Drives Are Very Reliable

One of the worst sounds in the world is that awful grinding noise associated with a failing hard drive, followed by a series of clicks. It typically indicates HDD failure is imminent and that you better backup your important data, if it's not too late already. Hey, it happens, but is bum luck solely to blame? Maybe not—the cloud backup specialists at Backblaze just released their HDD reliability report for the second quarter of 2016, and in it are initial (and promising) stats for newly introduced 8TB models.

Backblaze provides one of the few meaningful reports on HDD reliability. That's important because if you ask for advice on the web, you'll be met with anecdotal evidence about why a particular HDD or brand of HDD is garage or why it's the best ever. There's value in user reviews, of course, but there's more value in a report based on tens of thousands of HDDs performing backup chores over a long period of time, and that's what Backblaze provides.

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The outfit's been promising to add 8TB models to the mix, and it finally did. At first it added just 45 8TB HGST drives, noting that it didn't make economical sense to add a whole bunch of them for backup chores (it's running a business, after all). But then Seagate made available an 8TB at a "reasonable price" so Backblaze picked up and deployed over 2,700 of them in the second quarter, with more to come in Q3.

Things are looking good for the capacious drives so far. In 44,000 days of use, only four of the more than 2,700 Seagate ST800DM002 drives failed, which works out an annualized failure rate of 3.3 percent. And of the 8TB HGST HDS5C808ALE600, just two failed in 22,858 days of use, for an annualized failure rate of 3.2 percent.

For reference, here's how Backblaze describes its Annualized Failure Rate:
Some people question the usefulness of the cumulative Annualized Failure Rate. This is usually based on the idea that drives entering or leaving during the cumulative period skew the results because they are not there for the entire period. This is one of the reasons we compute the Annualized Failure Rate using “Drive Days”. A Drive Day is only recorded if the drive is present in the system. For example, if a drive is installed on July 1st and fails on August 31st, it adds 62 drive days and 1 drive failure to the overall results. A drive can be removed from the system because it fails or perhaps it is removed from service after a migration like the 2TB HGST drives we’ve covered earlier. In either case, the drive stops adding Drive Days to the total, allowing us to compute an Annualized Failure Rate over the cumulative period based on what each of the drives contributed during that period.
That said, Seagate's 4TB ST4000DX000 HDD is the company's go-to drive for the moment. It comprises just over half of the company's 68,813 HDDs with an Annualized Failure Rate of 2.8 percent. The company also really likes HGST's 2GB drives with their ultra low rate of failure (1.6 percent) but will be getting rid of those drives because it needs greater capacity.