Which is a more reliable storage medium, solid state drives (SSDs) or hard disk drives (HDDs)? To answer this question, cloud backup provider Backblaze provides some interesting drive failure statistics in its latest reliability report. So far, anyway.

Until now, Backblaze has never included SSD statistics in its reliability reports, as it only started using SSDs as boot drives more than two years ago, when it finally became possible to procure models with capacities around 200GB for less than the $50 we were paying for a 500GB HDD That's because I could now.

Now, two years later, Backblaze can compare SSD and HDD failure rates in the same environment. Of the 1,518 SSDs deployed, only two failed in the last quarter (January 1 to March 31, 2021), for an annualized failure rate of 0.58%. [On the other hand, 44 out of 1,669 HDDs failed during the same period, for a much higher annualized failure rate of 10.56%.

Backblaze also provides lifetime annualized failure rates for HDDs and SSDs from April 20, 2013 to March 3, 2021. Over the past eight years, Backblaze experienced 559 HDD failures with an annualized failure rate of 6.04%, compared to 8 SSD failures with a failure rate of only 0.65%.

Simply put, "SSD drives fail less often than HDD drives," Backblaze says, "which ignores one key factor: the failure rate of SSD drives is only 0.65%.

"Focusing on the age of each cohort could crack the 'SSD drives are better' hypothesis," Backblaze said.

The average age of SSDs included in the most recent reliability report was only 12.7 months, while the average age of HDDs deployed as boot drives was 49.6 months; the oldest SSD in Backblaze's stable environment was 30 months, while the youngest HDD was 24 months The oldest HDD in the Backblaze stable was 96 months old, and the youngest was 24 months old. (And the oldest HDD is 96 months old, or 8 years.) ) [This is an important data point when evaluating storage reliability and drive failure statistics.

"Essentially, the age timelines for SSD and HDD drives do not overlap much, and drive failure rates generally increase as the drives get older. Given these two factors, the conclusion that SSDs fail less frequently than HDD drives is not as clear-cut as it first seems," Backblaze states.

There is another aspect that Backblaze does not discuss in much detail: if you use SSDs to perform frequent backups, this becomes a more significant factor. If you are buying an SSD for a gaming PC, this is less important (although you should consider endurance ratings in terms of terabytes written (TBW) when looking for the best SSD for gaming in general).

Perhaps for that reason, Backblaze does not use SSDs to store customer data. However, according to the company, calling SSDs boot drives is a "misnomer" and they are also used to store log files for system access and diagnostics. In other words, they regularly read and write data and delete files.

So what do we get? Initially, SSDs seem to be less prone to failures than HDDs, at least in ultra-fast boot environments. However, more time and statistics are needed for a better comparison with HDDs, and Backblaze says it plans to study the initial failure statistics for each storage medium in the closer future and publish the results within a few months.