High capacity hard drives fare well in Backblaze's 2017 HDD reliability report

Having a hard drive go bad is never fun, and the higher the capacity, the more of a potential headache it can be, assuming you're actually using all that space. With that said, however, a new report from cloud backup provider Backblaze suggests that 8TB and higher capacity hard drives are fairly reliable.

Backblaze released another HDD reliability report, this time with stats from both the fourth quarter of 2017 and for the entire year. Given the varied spread of drives, there is no single, definitive takeaway from the results. Nevertheless, there are some interesting things to note.

Let's start with Seagate. The company has been somewhat of a punching bag in the comments section whenever we report on Backblaze's stats. That isn't likely to change with this latest report, which shows that Seagate's 4TB ST400DM005 HDD has annualized failure rate of 29.08 percent, based on its performance in the fourth quarter. However, that's based on a single hard drive failure, and the way Backblaze crunches its numbers.

"Quarterly failure rates can be volatile, especially for models that have a small number of drives and/or a small number of drive days. For example, the Seagate 4 TB drive, model ST4000DM005, has a annualized failure rate of 29.08 percent, but that is based on only 1,255 drive days and 1 (one) drive failure," Backblaze explains.

Backblaze employed 60 of that particular HDD model and saw one of them fail during the fourth quarter. Seagate's two other 4TB models, the ST4000DM001 and ST4000DM000, with annualized failure rates of 9 percent and 2.89 percent, respectively.

That latter failure rate is based on 32,070 HDDs representing 2,969,705 drive days. Backblaze employs more 4TB ST4000DM000 drives than another model or capacity. So, take from that data what you will.

As to the higher capacity drives, Backblaze also uses 5TB, 6TB, 8TB, 10TB, and 12TB HDDs from various manufacturers. Back in May of last year, we noted that Backblaze's stats made a strong case for 8TB models. The latest report shows more of the same. Here is a look:

The highest annualized failure rate among the bunch is 2.01 percent, which is attached to Seagate's 12TB ST12000NM007 HDD. All of the other 8TB and higher models have failure rates ranging from 0 percent to 1.22 percent. It's a limited sample set, but out of the five different 8TB or larger HDD models totaling 32,767 HDDs in all, the average failure rate is 1.07 percent.

Compare that with an average failure rate of 6.35 percent for the eight 4TB models, or 3.1 percent if we remove the ST4000DM005 and its 29.08 percent failure rate from the equation.

Here are some further observations, made by Backblaze:

• The failure rates for both of the 6TB models, Seagate and WDC, have decreased over the years while the number of drives has stayed fairly consistent from year to year.
• While it looks like the failure rates for the 3TB WDC drives have also decreased, you’ll notice that we migrated out nearly 1,000 of these WDC drives in 2017. While the remaining 180 WDC 3TB drives are performing very well, decreasing the data set that dramatically makes trend analysis suspect.
• The Toshiba 5TB model and the HGST 8TB model had zero failures over the last year. That’s impressive, but with only 45 drives in use for each model, not statistically useful.
• The HGST/Hitachi 4 TB models delivered sub 1.0 percent failure rates for each of the three years. Amazing.

If there is a takeaway to be had, it's the same as always—be sure to back up your data, and keep multiple backups of the especially important stuff.