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Backblaze reveals failure rates for hard drives in 2021, releases an SSD report for the first time: Digital Photography Review


Last month, cloud storage and data backup company Backblaze released its 2021 Annual Report for hard drive failure rates. Like in previous years, the report focused on failure rates for hard disk drives (HDD). However, yesterday, for the first time, Backblaze released a special follow-up to its 2021 Annual Report focused on solid-state drives (SSD).

Looking first at the standard report on HDD storage, Backblaze ended 2021 with a total of 203,928 data drives under its management. All the data drives use HDD technology. This venerable storage technology stores and retrieves digital data using magnetic storage. Spinning platters are paired with magnetic heads to read and write data. Hard drives like this can fail, and every year, given the sheer number of drives Backblaze manages, hundreds, or even thousands, of drives fail.

Of the 203,928 data drives, Backblaze removed 409 from consideration because they were used either for testing purposes or the company didn’t have at least 60 samples of that drive in use. That leaves 202,759 hard drives. Of these, 1,820 total drives failed during 2021. Backblaze measures failure rate by annualized failure rate. AFR = (drive failures / (drive days / 365)) * 100. Of the considered drives, a 6TB Seagate (model ST6000DX000) had the lowest failure rate of any drive model, with an annualized failure rate (AFR) of only 0.11%. Backblaze notes that this is particularly impressive given that this model is the oldest in its fleet, with an average age of 80.4 months. As Backblaze says, these drives are ‘thumbing their nose at the tail end of the bathtub curve.’

A pair of drive models added for 2021 are both performing well. The 16TB WDC drive (model WUH721816ALE6LO), with an average age of 5.06 months, has an AFR of 0.14%. The 16TB Toshiba drive cohort (model MG08ACA16TE) has an AFR of 0.91%.

The total AFR for 2021 for all Backblaze’s drive models was 1.01%, which is slightly higher than in 2020 when the AFR was 0.93%. However, 1.01% is considerably lower than 2019’s AFR of 1.89%. Overall, HGST and WDC are the best performers over the last three years, with AFR under 0.5% in all but a couple of quarters. Toshiba comes up next with Seagate drives offering the highest AFR. Of course, when you dig into the data, you find that there are drives from each manufacturer that perform well.

To dig further into the numbers and download all data, check out the full report. Now, let’s turn our attention to the new SSD report. Whereas Backblaze uses HDDs for its data storage, the SSDs in the report are exclusively used as boot drives. Starting in Q4 2018, Backblaze began replacing failed HDD boot drives with SSDs. For Backblaze, boot drives also store log files and temporary files produced by the storage server. Every day, a boot drive reads, writes and deletes files. As of the end of 2021, Backblaze was using 2,200 SSDs.

Looking at the annual failure rate for SSDs overall, it’s similar to HDDs. In 2019, which was just a single quarter, AFR was 0.86%. In 2020, it was 0.78%. Last year, it increased a bit to 1.22%. However, there are two glaring outliers in 2021. The Crucial (CT250MX500SSD1) and Seagate (ZA2000CM10002) SSDs failed at rates of 43.22% and 28.81%, respectively. Why? Well, unlike the HDD report, there’s a difference in sample size. Backblaze uses only 20 Crucial drives, and they were all installed in December. While there’s a high AFR, there’s a low sample size and a wide confidence interval. The situation is more extreme with the Seagate drive in question. There are only four of them in use and one of them failed.

In general, not many SSD models are used in significantly high numbers. Backblaze uses 1,090 of the Seagate ZA250CM10003 drive and it had a 1.04% AFR in 2021. The company also employs 562 Seagate ZA250CM10002 drives. Its AFR was even more impressive at 0.36%. Backblaze has 250 Dell DellBoss VD SSD drives. Not a single one failed.

If you dig around in Backblaze’s data, there are some anomalies it wants to point out. Two SSD models show up in the data aren’t in the report, including the Samsung 850 EVO 1TB and the HP SSD S700 250GB. They were used for internal testing or specific migration tasks.

While 2,200 SSDs is a small number of drives, there’s still plenty of data worth considering. Backblaze will continually add SSD boot drives to its operation, improving the quality of the data. Backblaze is also considering adding SSDs that it uses in other types of servers in its environment to the 2022 annual report. To read the full 2021 Annual Report: SSD Edition, visit Backblaze.


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