Are SSDs more reliable than HDDs? This research may have the answer

Image: Getty Images/Pannonia

According to cloud storage company Backblaze, solid state drives (SSDs) are more reliable than hard disk drives (HDDs) — at least for certain use cases. But that might not make much of a difference when deciding what type of memory you should buy.

The company wanted to settle a debate earlier this year about whether HDDs or SSDs are more reliable. Backblaze offers a cloud backup service for laptops and computers and offers its B2 cloud storage for businesses.

It uses a mix of SSDs and HDDs as storage server boot drives in the Backblaze Cloud Storage platform. Since 2018, it has replaced failed boot HDD drives mostly with 2.5-inch SSDs (some are M.2 form factor drives). Backblaze’s SSD/HDD drives boot its storage servers and store log files and temporary files created by the storage server. Today, Backblaze has over 2,500 SSDs (a mix of Crucial, Dell, Micron, Seagate, and Western Digital) and stores over two exabytes of data.

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The company measures the reliability of SSDs and HDDs by tracking the annualized failure rate (AFR) of SSDs and HDDs to shed light on the “previously opaque world of hard drive failure rates” and, of course, to stimulate debate about the technologies behind its service.

To account for the age differences between the older HDDs and the newer SSDs it was comparing, last year it released the SSD and HDD AFRs with “endurance control”. It turned out that SSDs failed less often, but only slightly. (The problem with his data was that HDD failure rates increased dramatically after five years and there was no five-year data for SSDs yet.)

“The difference alone certainly wasn’t enough to justify the additional expense of purchasing an SSD over an HDD,” the company concluded at the time, noting that when purchasing either technology, the cost, required speed, power consumption, and the form factor should be better considered.

Now, with a year more data on SSDs aged five, one comes to a different conclusion – albeit with some caution.

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The lifetime AFR for HDDs and SSDs was 1.83% and 1.05% respectively in year four, while the gap widened in year five: 3.55% for HDDs versus 0.92% for SDDs. The lifetime AFR for HDDs at years six, seven, and eight was 5.23%, 6.26%, and 6.93%, respectively. It remains to be seen how its SSDs will fare over these years.

“At this point, we can reasonably claim that SSDs are more reliable than HDDs, at least when used as boot drives in our environment,” it says.

Backblaze adds: “It is very certain that the failure rate of SSDs will increase at some point. It’s also possible that the SSDs will eventually hit the wall, perhaps as they start to reach their media wear limit.”

However, that only eliminates one of the variables consumers need to weigh when purchasing storage, with price remaining a key factor, as a 1TB SSD costs at least twice as much as a hard drive of the same capacity.


Source: Backblaze

Backblaze points out that using failure rate as a factor in your decision is actually questionable. Once age and drive days were controlled, the two drive types were similar, and the difference alone certainly wasn’t enough to justify the additional expense of purchasing an SSD over an HDD. “At this point, you’d be better off deciding based on other factors: cost, required speed, power, form factor requirements, and so on,” it suggested.

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