A study of 443,000 Backblaze drives ranks HGST and WD more reliable than Seagate and Toshiba
An IEEE study published in August 2026 analyzes 443,156 Backblaze drives across 1.66 million drive-years and corrects for age bias: under comparable conditions, HGST and WD fail about half as often as Seagate and Toshiba. For a NAS or homelab, the lesson is less about brand than about temperature and capacity.
August 2026. A peer-reviewed IEEE study by Christoph Siemroth (University of Essex) and Yeomyung Park (Sungkyunkwan University) analyzes 443,156 Backblaze hard drives. 2013 through Q2 2025. The covered period, totaling more than 1.66 million drive-years. Under comparable conditions. HGST fails at about 41% of Seagate’s rate, WD at 52%, and Toshiba at 107%.
For anyone buying drives for a NAS, the conclusion fits in one sentence: raw failure-rate comparisons lie, and once the biases are corrected, Seagate and Toshiba fail roughly twice as often as WD and HGST.
Why the raw rate lies
The classic trap in Backblaze’s quarterly reports is comparing AFR (annualized failure rates) directly across manufacturers. The problem: the fleets are not the same age. HGST dominated new installs in 2014, Seagate supplied most drives from 2015 to 2020, Toshiba was the top installer in 2023, and WD in 2024.
Comparing brands without correction pits an old fleet against a new one. A drive’s failure risk depends on its service age, capacity, form factor, temperature, and technical generation — a recent helium-filled drive is not comparable to an older air-filled model.
The study corrects these biases with duration regressions, and also treats drives removed without a recorded failure — 146,943 units, or 31% of the sample — as right-censored data rather than as eternally healthy drives. That rigor is what separates it from a simple failures-over-days ratio.
The ranking, once corrected
With Seagate as the reference, the adjusted failure rates produce a clean ranking. HGST comes first at 41% of Seagate’s rate. WD follows at 52%, a gap the authors deem statistically significant. Toshiba finishes last at 107%, just above Seagate.
Put simply: Seagate and Toshiba fail roughly twice as often as HGST and WD in the fleet studied. But the devil is in the trajectory. Seagate starts with a higher rate on young drives, then ages relatively gently. Toshiba does the opposite: its monthly failure rate quadruples after 60 months of service, reaching 5 to 6 failures per 1,000 drives per month between 50 and 100 months, while the other brands stay under 2.5.
In other words, a brand can look fine at install time and then degrade sharply late in life. That is exactly the information a NAS buyer wants — and exactly what the raw rate does not reveal.
What actually matters: temperature and capacity
The study delivers two actionable levers, far more useful than a brand ranking.
First, temperature. Each additional degree Celsius of average drive temperature raises the calculated failure rate by about 2.1%; over a ten-degree difference, the cumulative effect reaches 23%. This is not a threshold beyond which a drive dies, but a clear statistical relationship: a poorly ventilated NAS whose drives run hot wears them out faster. Controlled cooling remains the best reliability investment you can make.
Second, capacity. Each additional terabyte is associated with a failure-rate decline of about 3.4%. The authors attribute this partly to the growing share of recent designs — helium-filled enclosures, improved heads — among high-capacity models. Capacity itself does not make a drive more reliable; it is a marker of a newer generation.
Finally, the study finds an improvement per install year at every manufacturer: Seagate drops about 10 to 11% per deployment year, Toshiba and WD sometimes more. A brand evaluated over twelve years does not represent a fixed trait — platforms, motors, heads, and firmware all evolve.
What it changes at purchase time
The ranking has a counterintuitive consequence: HGST, the winner, no longer exists as a new-drive brand. Western Digital acquired HGST in 2012 and gradually retired the name — its most reliable enterprise drives, such as the Ultrastar line, descend directly from HGST engineering. When a study says “HGST is the most reliable,” what you actually buy is a WD Ultrastar or an equivalent from that lineage, not a drive stamped HGST that no longer ships new.
The second consequence concerns size. Drives of 20 TB and above, mostly helium-filled, show lower failure rates in the study than smaller, older models. Buying “small to try it out” is therefore a false instinct: a recent high-capacity drive is statistically more reliable than an old entry-level model — provided the enclosure cools it properly, which loops back to temperature.
The third is exactly that: airflow. Home NAS boxes — often compact enclosures without dedicated forced airflow — are the worst case: tightly packed drives heating up in a living room. The study quantifies the effect: +1 °C of average temperature costs about 2.1% more failures, or 23% across ten degrees. A well-placed enclosure fan is a better reliability investment than any brand difference — and it costs a few euros, not lost terabytes.
One caution remains. The study covers enterprise drives run in data-center conditions, not desktop drives; it lacks comparable per-model workload data, and only 0.52% of drives exceeded ten years of service. It therefore illuminates a drive’s early and middle years — the window that matters for a NAS refreshed every five years — more than its full theoretical lifespan.
Verdict
If you are buying drives for a NAS or homelab, the adjusted ranking gives a simple rule: favor WD — or designs from the HGST lineage — and be wary of Toshiba for arrays you intend to keep beyond five years, since its rate spikes after 60 months. Seagate holds up on young drives but starts higher.
If budget is the real constraint, the lesson lies elsewhere: before arguing over brand, fix your ventilation — ten degrees cooler is worth 23% fewer failures — and buy recent, high-capacity drives, which are statistically more reliable than cheap older hardware.
If you follow Backblaze’s quarterly reports, remember the study’s limits: it describes a data-center fleet, not desktop drives, and only 0.52% of drives exceeded ten years of service. The results illuminate reliability in a drive’s early and middle years, not its full lifespan. Use them to choose, not to predict a specific drive’s death.