A question I get asked a lot is, "which is the best hard drive to buy?" It's a tough question to answer because, unless you have tens of thousands of drives spinning, you end up relying on what the manufacturers say or personal experience drawn from a limited sample set (anecdata).
But there is a company that has tens of thousands of drives in operation, and who keeps a close eye on failure rates. That company is cloud backup firm Backblaze.
Backblaze has published its Q1 2020 hard drive stats, which looks at the failure rates for 129,764 hard drives from HGST, Toshiba, and Seagate (this figure excluded test drives and drive models where Backblaze had less than 60 in operation).
The data gives us an interesting insight into reliability.
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Something that stands out immediately is a lot of Seagate failures over the period. That said, Backblaze has a lot of Seagate drives, so it makes more sense to look at the AFR, or Annualized Failure Rate, which is calculated as follows:
AFR = (Drive Failures / (Drive Days / 366) * 100
Note: Backblaze goes into detail as to why it uses this figure in the report.
While the average AFR for the reporting period was 1.07 percent, the lowest since Backblaze started tracking it in 2013, it is significantly lower than the Q1 2019 AFR of 1.56 percent.
However, the AFR for the worst-performing Seagate drive -- the 4TB ST4000DM000 was 1.42 percent, closely followed by the 12TB ST12000NM0008 with an AFR of 1.41 percent.
Interestingly, two HGST drive models -- the 8TB HUH728080ALE600 and the 12TB HUH721212ALE604 -- which both have a reasonably high number of "drive days" (the cumulative number of days the drives have been in operation) experienced no failures.
Backblaze had predicted back on Q1 2019 that is would have downscaled the number of 4TB drives it had in use by the end of the year to about 15,000. In reality, it still has about 35,000 in operation.
Another Q1 2019 prediction was that Backblaze would be testing 20TB drives, along with HAMR based drive from Seagate and/or MAMR drives from Western Digital. It currently has none of these.
So, the bottom line is that drives seem to be getting more reliable, but that some are more reliable than others.