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SSD or HDD: Which is more reliable?

Backblaze, a provider of cloud storage and backup services, has published a report based on data from the SSDs it has used since late 2018 on its Backblaze Cloud Storage platform. At the end of last June, they had a total of 2,558 SSDs.

One point to emphasize is that these are SSDs that are only used as storage server boot disks by Backblaze, not as storage solutions in their own right. However, they do store event histories (log files) and temporary files produced by the storage servers.

So far, Backblaze has primarily published reports on the condition, and reliability, of the hard drives used in its data centers. With some hindsight gained, the time has come for a showdown, and for hard drives also used as a bootable medium.

SSDs are primarily 2.5-inch SATA drives, with only several hundred M.2-type SSDs. In comparison with hard disks, and for annualized failure rates, it appears that solid state disks (SSD) and hard disks (HDD) observe a similar curve during the first years of activity, but SSDs are less often affected by failures.

Big advantage for SSDs

After four years, hard drives show a failure rate of 1.83%, while SSDs show a failure rate of 1.05%. Subsequently, Backblaze looked forward to the evolution of the SSD curve. Thanks to Q2 2022 data, the trend is emerging and is clearly in favor of SSDs with trajectories for the curves that differ.

In year five, the failure rate for solid state drives drops below 1% to 0.92%, while that of hard drives rises from 1.83% to 3.55%. Thereafter, the failure rate of hard drives continues to rise and has reached almost 6.5% after eight years of activity.

“At this point, we can reasonably say that SSDs are more reliable than HDDs, at least when used as a boot disk in our environment,” states Backblaze. Of course, it will be necessary to follow the evolution of the trend over time and SSDs can suddenly stop.

This type of comparison has limitations due to the sample of solid state disk models, that is, a dozen between the brands Crucial, Dell, Micron, Seagate and WDC, in addition to a single use as a bootable media that minimizes the volume of data.

Hard drives are a rotating magnetic disk memory device. SSDs are flash memory without any mechanical components, and manufacturers provide warranty information. The fifth year is often taken as a reference (or for the total number of bytes written with advantage for large capacities).

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