Read on 2026-10-16. The figures come from drives running in a data center, which the source itself says is not how consumers use drives. They show how failure rates behave across a large fleet, not how long your drive will last.
What a failure rate needs
Backblaze, in its post “How Long Do Disk Drives Last?” (December 17, 2021), says that the term failure rate alone is not very useful as it is missing the notion of time. It adds that when it produces its quarterly and annual Drive Stats reports, it calculates and publishes the annualized failure rate (AFR), so that all failure rates are translated to be annual and different cohorts of drives can be compared regardless of timeframe.
Backblaze, in its post “NAS RAID Levels Explained”, says that with an annual failure rate (AFR) of 1%, out of a sample of 100 drives, we'd expect one of them to fail in the next year.
The 2025 numbers
Backblaze, in its post “Backblaze Drive Stats for 2025” (February 12, 2026), says that as of the end of 2025, Backblaze was monitoring 349,462 hard drives used to store data. It adds that the annual AFR for 2025 finished at 1.36%, down from 1.55% in 2024. It also says that the lifetime AFR, for the reporting period ending December 31, 2025, is 1.30%.
The same post says that its Q4 2025 report lists the HGST HUH728080ALE600 8TB drive model at an AFR of 10.29%, and that this model has 1,073 drives in total, which is less than one Vault.
Backblaze, in its bathtub curve post (October 15, 2025), says that over the years it has really only seen model-by-model variation, so if you get a lemon of a drive and you've added a lot of them, you may have a chunk of drives failing all at once.
How failure changes with age
Backblaze, in its 2021 post, says that the initial drive life study was done with 25,000 disk drives and about four years of data, while the later study included data from over 200,000 disk drives, many of which have survived six years and longer. It adds that about 90% of the drives it owns have lasted four years and 65% are living longer than six years. It also says that a reasonable estimate of the median life expectancy is six years and nine months, an estimate extrapolated from the data through six years because it did not have enough data to be confident beyond six years.
The 2025 post compares the age at which the failure rate peaked in three analyses.
| Analysis | Peak AFR | At drive age |
|---|---|---|
| 2013 | 13.73% | about 3 years, 3 months |
| 2021 | 14.24% | 7 years, 9 months |
| 2025 | 4.25% | 10 years, 3 months |
The same post says that the 2025 analysis reported on 317,230 drives, and that when a drive is between zero and one years old, the AFR barely cracks 1.30%. It adds that drives are getting better—or, more precisely, the Drive Stats dataset says that Backblaze's drives are performing better in data center environments. It also says that there are usual caveats about how it uses drives vs. how consumers use drives.
Drives inside a NAS
Backblaze, in its post “NAS Life Expectancy: How to Extend NAS Longevity”, says that it is crucial to differentiate between the life expectancy of a NAS device and that of the hard drives within the device. It adds that while the NAS itself may continue to function, the hard drives that are subjected to intense read/write operations often have a shorter lifespan. It also says that implementing a regular schedule to check drive health and replacing unhealthy or borderline drives proactively can prevent data loss.
What the source tells you to do
Backblaze, in its 2021 post, says that every hard drive you buy will fail at some point, and it could be in one day or 10 years. It adds that the correct answer to how long to assume a drive will last is to always have at least one backup and preferably two, keep them separate, and check them often, which is the 3-2-1 backup strategy.
Expected failures from an AFR
Failures per year
Type an annual failure rate from a report and the number of drives you run.
- Failures expected per year
- Chance that at least one fails in a year
Expected failures = drives x AFR. The chance of at least one failure is 1 minus the chance that every drive survives, with each drive treated alike and independent. A fleet's AFR is an average over many drives and says little about one drive. Nothing you type leaves your browser.
The dataset behind these reports is on Backblaze's Hard Drive Test Data page.
Backblaze, in its 2025 Drive Stats post, says that the Drive Stats dataset can be downloaded and used for free, on the conditions that you cite Backblaze as the source, accept that you are solely responsible for how you use the data, and do not sell the data itself.
Sources
Checked on 2026-10-16 against Backblaze: How Long Do Disk Drives Last?, Backblaze: Drive Stats for 2025, Backblaze: Are Hard Drives Getting Better?, Backblaze: NAS Life Expectancy, Backblaze: NAS RAID Levels Explained. Read the source again before you rely on a number, because posts get updated and drive models change.
Related guides
- SSD lifespan: TBW and P/E cycles: How to read endurance numbers on a spec sheet, with a write-budget calculator.
- RAID levels explained: Striping, mirroring and parity, and what each level tolerates.
- NAS or external hard drive: What each one is and what neither protects against.