Backblaze Hard Drive Reliability: What Years of Drive Data Really Tell Home Users
Backblaze publishes one of the most useful public datasets in storage: daily health records from hundreds of thousands of drives running in its data centers. I wanted to know what that data actually tells a home user shopping for backup, NAS or bulk-storage drives, so I pulled the public Drive Stats data into my own deterministic analysis instead of relying on a single quarter or a few headline numbers.
Quick answer: Backblaze data is extremely useful, but it does not support a simple conclusion like “Brand X is best.” The better lesson is that specific drive models, capacity generations, age, sample size and time in service matter much more than the logo on the label. Some 20TB+ models are posting very low failure rates, while several older 8TB–14TB models are showing substantially higher AFRs. The long-term trend matters more than any one quarter.
If you are deciding what kind of hard drive to buy in the first place, start with my Hard Drive Know IT Guyde. This article is the deeper reliability layer behind that buying decision.
What Backblaze Drive Stats Actually Measure
Backblaze has published Drive Stats data since 2013. Every day, it records a snapshot of each operational drive in its data centers, including the model, serial number, failure flag and S.M.A.R.T. attributes. One drive operating for one day contributes one drive-day to the dataset.
The metric most people focus on is AFR, or annualized failure rate:
AFR = failures × 365 ÷ drive-days × 100
AFR is useful because it normalizes failures against exposure time. Ten failures among 100 drives is very different from ten failures among 40,000 drives, and drive-days help capture that difference.
Backblaze also applies minimum sample thresholds before including a model in its published tables. For quarterly analysis, a model needs more than 100 drives at the end of the quarter and more than 10,000 drive-days during the quarter. Annual and lifetime tables use higher thresholds. Those rules matter because a tiny sample can produce a dramatic AFR from only one or two failures.
Backblaze’s official Hard Drive Test Data page provides both downloadable files and a public Apache Iceberg version of the dataset. At the time I ran this analysis, the Iceberg table contained daily records through June 30, 2026. Backblaze’s latest published quarterly commentary was still its Q1 2026 report, so the Q2 figures below are my calculations from the public raw dataset, not a published Backblaze Q2 report.
The Big Trend: Backblaze Is Storing Much More Data on Larger Drives
The fleet itself has changed dramatically. In my analysis, Backblaze had about 206,928 active drives at the end of 2021, representing roughly 2.25 exabytes of raw capacity. By June 30, 2026, the dataset showed about 355,238 active drives and approximately 5.71 exabytes of raw capacity.
That is the first important reliability lesson: the number of drives grew substantially, but capacity grew much faster. Backblaze has been steadily replacing smaller drives with higher-capacity models.
Backblaze’s own Q1 2026 report makes that shift even clearer. Of 10,220 drives deployed during the quarter, 9,404 were larger than 20TB. Backblaze reported that its 20TB+ pool had an AFR of about 0.85% at that point.
My raw capacity-cohort analysis shows the same transition. The 20TB+ category was effectively nonexistent in the dataset until 2023. By Q2 2026, it represented more than 8.4 million drive-days in a single quarter.
Are 20TB, 22TB and 24TB Hard Drives Reliable?
So far, the answer is encouraging—but not uniform.
In my Q2 2026 analysis, these large-capacity models all met the same quarterly qualification rule of more than 100 drives and more than 10,000 drive-days:
| Model | Capacity | Drives | Q2 2026 AFR |
|---|---|---|---|
| WDC WUH722222ALE6L4 | 22TB | 45,556 | 0.555% |
| Toshiba MG11ACA24TE | 24TB | 9,597 | 0.575% |
| WDC WUH722626ALE6L4 | 26TB | 6,958 | 0.947% |
| Toshiba MG10ACA20TE | 20TB | 25,171 | 1.103% |
| Seagate ST24000NM002H | 24TB | 9,482 | 3.474% |
That spread is exactly why capacity alone is not enough. A 24TB label does not tell you the reliability story. In this quarter, one qualified 24TB model was under 0.6% AFR while another was over 3.4%.
It is also too early to treat every 20TB+ model as a mature long-term winner. These drives are younger than the 8TB–16TB models that have accumulated years of service. What is encouraging is that very large drives are not automatically showing worse reliability simply because they hold more data.
Long-Term Results Matter More Than a Single Quarter
A quarterly table is useful for spotting changes, but I care more about models that repeatedly qualify over many quarters. That reduces the chance that one unusually good or bad quarter dominates the conclusion.
Here are several models with long-running qualified histories in my 2021–Q2 2026 analysis:
| Model | Capacity | Qualified Quarters | Combined AFR | Quarterly Range |
|---|---|---|---|---|
| WDC WUH721414ALE6L4 | 14TB | 22 | 0.545% | 0.000%–1.073% |
| Seagate ST16000NM001G | 16TB | 22 | 0.673% | 0.406%–1.751% |
| Toshiba MG07ACA14TA | 14TB | 22 | 1.079% | 0.557%–1.939% |
| Seagate ST12000NM001G | 12TB | 22 | 1.010% | 0.360%–1.387% |
| Seagate ST12000NM0008 | 12TB | 22 | 2.296% | 0.848%–3.454% |
| HGST HUH721212ALN604 | 12TB | 22 | 3.105% | 0.337%–7.628% |
| Seagate ST14000NM0138 | 14TB | 22 | 5.884% | 2.431%–10.245% |
| Seagate ST10000NM0086 | 10TB | 22 | 4.858% | 1.004%–12.318% |
The combined AFR figures in this table are my aggregate calculations across the qualified quarters shown; they are not Backblaze’s published lifetime AFR figures.
The important point is not that one manufacturer wins. The same manufacturer can have one excellent model and another model with a much higher failure rate. That is why I would rather shop by model family, workload, capacity and current price than by brand loyalty.
Some Older Drive Models Are Posting Higher AFRs
The Q2 2026 data also shows several qualified models with much higher AFRs:
- HGST HUH721212ALN604 12TB: 7.628% AFR in Q2 2026.
- Seagate ST14000NM0138 14TB: 8.265%.
- Seagate ST10000NM0086 10TB: 9.751%.
- WDC WUH721816ALE6L0 16TB: 4.344%.
I would not interpret those numbers as proof that every drive of those models is about to fail. Some of these populations are old, and aging cohorts can naturally show higher failure rates. But if I were buying used or recertified enterprise drives, these are exactly the kinds of model histories I would want to know before deciding whether a low price is worth the risk.
Why Zero Failures Can Still Be Misleading
A model can record zero failures in a quarter and still not be the best choice. Sample size is the reason.
For example, a model with 500 drives and no failures has much less evidence behind it than a model with 40,000 drives and a 0.6% AFR. A single failure in a small population can also make AFR jump dramatically. Backblaze explicitly calls this out in its own reports.
That is why this analysis keeps the qualification thresholds and looks across multiple quarters. I am much more interested in a model that has stayed consistently low across millions of drive-days than one that happens to post a perfect quarter with a small population.
Can You Use Backblaze Data to Pick a NAS Drive?
Yes—but only as one input.
Backblaze runs drives in large data-center storage systems. A home NAS, Unraid server or desktop backup enclosure has a different environment, workload, vibration profile, cooling setup and replacement cycle. Backblaze also buys at enterprise scale and may deploy model families that are not the exact retail SKU you are considering.
Still, the data is valuable because it answers a question that normal reviews cannot: what happens when thousands of the same drive model accumulate millions of days of real service?
For a NAS purchase, I would combine Backblaze history with the practical factors in my Hard Drive Know IT Guyde: NAS-rated versus desktop drives, CMR versus SMR, warranty, noise, workload rating, capacity and price per terabyte.
What This Means for Home Backup and Bulk Storage
For home users, I think the data supports five practical rules.
- Do not buy by brand alone. Model-level differences can be much larger than brand-level averages.
- Large-capacity drives are not automatically less reliable. Several 20TB+ models are currently performing very well in Backblaze’s fleet.
- Prefer mature evidence when the price difference is small. Millions of drive-days across many quarters tell me more than a launch review.
- A cheap used enterprise drive needs context. Age and model history matter, especially for older 8TB–14TB generations.
- Reliability is not backup. Even the best drive can fail. Keep multiple copies of important data.
For that last point, see my 3-2-1 backup article and the Cloud Storage Know IT Guyde. A reliable disk is one layer of a storage strategy, not the entire strategy.
Buying Paths: Where the Data Becomes Useful
I would use Backblaze data as a screening tool, then shop the drive category that matches the job. These links go to broad Amazon searches rather than pretending one exact model is universally best.
- Compare NAS hard drives on Amazon
- Compare 20TB hard drives on Amazon
- Compare 22TB hard drives on Amazon
- Compare 24TB hard drives on Amazon
- Compare large external hard drives on Amazon
As an Amazon Associate I earn from qualifying purchases.
What the Backblaze Data Does Not Tell Us
There are several limits I would keep in mind before turning AFR into a buying recommendation.
- Data-center use is not home use. Cooling, vibration, duty cycle and hardware are different.
- Fleet age matters. A newer high-capacity model has not yet lived through the same aging curve as a ten-year-old drive population.
- Model availability differs. Some Backblaze models are enterprise or hyperscale variants that may not be easy to buy at retail.
- AFR is a population statistic. It cannot predict when one specific drive will fail.
- Quarterly AFR can be volatile. Small populations and a few failures can move the percentage sharply.
- Reliability is only one buying factor. Warranty, acoustics, power, workload rating, interface, CMR/SMR behavior and price per terabyte also matter.
My Hard Drive Buying Takeaway
The strongest lesson I get from years of Backblaze data is that there is no permanent “best hard-drive brand.” There are strong and weak models inside the same manufacturer, and those results change as drive generations age and new capacities enter the fleet.
If I were buying today, I would first choose the right type of drive for the job, then compare current models and pricing, and finally use long-term fleet data as another signal before spending the money.
The encouraging part is that the move to 20TB, 22TB, 24TB and even 26TB drives has not produced evidence that bigger disks are inherently unreliable. Several of the largest populations in Backblaze’s current fleet are posting excellent numbers. That is good news for anyone trying to build a NAS, backup server or large media-storage system without filling it with a dozen smaller disks.
How We Built This Analysis
I did not manually copy numbers out of Backblaze blog tables. The analysis is built from Backblaze’s public daily Drive Stats dataset so it can be rerun as new data arrives.
Backblaze B2 ↓ Apache Iceberg table ↓ DuckDB + httpfs + iceberg ↓ Jimbot deterministic analyzer ↓ Quarterly / model trend JSON ↓ Markdown report ↓ Editorial interpretation ↓ WordPress article
The public dataset is exposed as an Apache Iceberg table in Backblaze B2. I query that table directly with DuckDB 1.5.5 using the httpfs and iceberg extensions.
The analyzer first locates the current Iceberg metadata snapshot, then reads the daily drive records. Each row represents one drive on one day. From those rows, the scripts calculate:
- quarterly fleet drive-days and failures;
- annualized failure rate;
- fleet size and raw capacity over time;
- capacity cohorts such as 8–13TB, 14–19TB and 20TB+;
- quarterly model-level drive counts, drive-days, failures and AFR;
- multi-quarter model histories using Backblaze-style minimum sample thresholds.
For the model-level analysis, I normalize obvious model-name variants before aggregation. That matters because the raw dataset can contain the same WD model with and without a manufacturer prefix or with inconsistent spacing.
A simplified version of the model aggregation looks like this:
SELECT
model,
COUNT(*) AS drive_days,
SUM(failure) AS failures,
100.0 * SUM(failure) * 365 / COUNT(*) AS afr
FROM drive_stats
WHERE date BETWEEN quarter_start AND quarter_end
GROUP BY model;
The analysis then applies the same basic quarterly qualification rule Backblaze publishes: more than 100 drives at quarter end and more than 10,000 drive-days in the quarter.
The important editorial rule is that the script does the arithmetic and qualification; I decide what the numbers mean for a home user. That separation makes the analysis reproducible without pretending that a data-center AFR automatically translates into a retail buying recommendation.
Backblaze remains the original source for all Drive Stats data used here. You can explore the official dataset and methodology at Backblaze Hard Drive Test Data and read the company’s Q1 2026 Drive Stats report.
FAQ
What is a good hard drive AFR?
Lower is better, but AFR only makes sense with sample size and age. I would rather see a model stay near or below 1% across millions of drive-days and many quarters than see a tiny population record zero failures once.
Does Backblaze prove one hard-drive brand is the most reliable?
No. The model-level results vary substantially within each manufacturer. The data is much more useful for evaluating specific drive families and generations than for declaring one permanent brand winner.
Are 20TB and larger hard drives reliable?
The current data is encouraging. Several 20TB+ models have low AFRs across large populations, but many of these drives are still relatively young. Their long-term aging behavior will become clearer as more quarters accumulate.
Can I use Backblaze results to choose a drive for Synology, Unraid or another NAS?
Yes, as one input. Also consider NAS compatibility, CMR versus SMR, warranty, workload rating, acoustics, power and price. Backblaze’s data-center environment is not identical to a home NAS.
Is a drive with 0% AFR guaranteed to be reliable?
No. Zero failures can simply mean the population is small or the observation period is short. Sample size and drive-days are essential context.
Does RAID replace backup?
No. RAID can improve availability after a drive failure, but it does not protect against deletion, corruption, malware, theft, fire or a system-wide failure. Important data still needs independent backup copies.
How often will this analysis be updated?
The underlying analysis is designed to be rerun as Backblaze publishes new Drive Stats data. Jimbot runs the deterministic analysis on a quarterly schedule so this article can be reviewed against new fleet and model trends.
