What Backblaze Drive Failure Reports Actually Tell You

Backblaze's quarterly drive failure reports are the most cited reliability data in the storage industry. They are also frequently misread and misapplied. Understanding what the data actually measures — and more importantly, what it does not measure — is necessary before using it to make hardware purchasing or maintenance decisions. When applied correctly, Backblaze's data provides the most reliable public benchmark for comparing drive models. When applied incorrectly, it produces false confidence in the reliability of consumer desktop drives.

For the broader context of hardware failure statistics, see our PC hardware failure statistics guide and our SMART data and SSD failure prediction guide.

What Backblaze Actually Measures

Backblaze is a cloud storage and backup company. They run large storage pod arrays with 10,000+ drives per pod. Their failure reports cover:

The drives: Enterprise-grade HDDs (primarily Seagate Exos, Western Digital Gold/Ultrastar, Toshiba MG series) and enterprise SSDs used as boot devices and metadata storage. These are not consumer desktop drives. The closest consumer equivalents are the WD Red, Seagate IronWolf, and similar NAS-rated drives — but these are still different products optimized for different use cases than the enterprise drives in Backblaze's data.

The environment: Backblaze's storage pods are in purpose-built data center facilities with controlled temperature (typically 18–22°C), continuous airflow, and professional monitoring. Drives operate at lower temperatures than the same hardware would in a typical PC case. Cooler operating temperatures generally improve drive reliability.

The workload: Backblaze's drives handle storage pod workloads — large sequential writes and reads, moderate random I/O, 24/7 operation. This differs significantly from desktop PC workloads (frequent small random I/O, OS operations, application access patterns).

The metric: AFR (Annualized Failure Rate) — the percentage of drives in service that failed in a given period, annualized. A 1.5% AFR means 1.5 out of every 100 drives in the fleet failed within a year.

Reading the Quarterly Reports Correctly

Backblaze publishes detailed quarterly reports at backblaze.com/blog. The key data in each report:

Drives in service (DIS): The number of drives currently running. Large numbers (10,000+) produce statistically reliable AFR calculations. Small numbers (100–500) produce less reliable figures — even a few random failures or non-failures significantly affect the rate.

Drive hours: Total hours all drives of that model have been running. Used to calculate failure rate per unit time.

Failures: Number of drives that failed during the period. Backblaze's definition of failure: the drive is no longer readable and must be replaced.

AFR calculation: (Failures / Drive Hours) × (8760 hours per year) × 100 = AFR percentage

What to look for:

• Models with high drive counts (>1,000) and low AFR: statistically reliable, good candidates
• Models with low drive counts and very low AFR: may be lucky sample size, not reliable
• Models with consistent low AFR across multiple consecutive quarters: more reliable than any single quarter
• Models showing increasing AFR over time as drives age: bathtub curve showing end-of-life failure increase

The 2024–25 Backblaze SSD Data

Backblaze started publishing SSD failure data in 2023 as they expanded SSD deployment beyond boot drives. The 2024–25 SSD data is less mature (smaller sample size, fewer drive hours) than their HDD data but provides early directional evidence:

Key findings from recent Backblaze SSD reports:

• Enterprise SSDs in Backblaze's environment show very low AFR (0.3–0.8% for most models in their first 2 years)
• Seagate enterprise SSDs showed competitive reliability vs. Samsung and WD enterprise models
• Boot SSDs (typically smaller capacity, lighter write workload than storage drives) showed lower failure rates than storage-duty SSDs
• No QLC consumer SSDs appear in Backblaze's production data — their SSD data is enterprise TLC and MLC drives

What this means for consumer SSD selection: Backblaze's SSD data does not directly benchmark the Samsung 870 EVO, WD Black SN850X, or Crucial P5 Plus that go into business desktop PCs. The data shows enterprise TLC drives are reliable at low to moderate write loads, which is consistent with manufacturer TBW specifications.

Limitations for Desktop/Laptop Use Cases

The gap between Backblaze's data and consumer desktop drive reliability:

Temperature: Backblaze drives operate at 20–35°C. Desktop PC drives operate at 30–70°C depending on case airflow and workload. Higher temperatures accelerate failure rates for both SSDs (NAND wear) and HDDs (mechanical wear). A drive with 1.5% AFR in Backblaze's cool environment might show 2–3% AFR in a warm desktop PC case.

Vibration: Backblaze's storage pods have multiple drives running simultaneously, generating vibration that HDDs are sensitive to. Desktop PCs typically have 1–2 drives with less ambient vibration. This may make HDD failure rates slightly lower in desktops than in Backblaze's environment.

Workload type: Backblaze's streaming workloads (sequential I/O) are less damaging to HDDs than the mixed random I/O typical of desktop operating system drives. Desktop OS drives experience more random access, which is harder on HDD actuator mechanisms.

Drive age distribution: Backblaze actively removes old drives and replaces them, so their fleet has a different age distribution than a typical business that runs drives until failure. Their AFR numbers include relatively fresh drives; a business running drives to 5+ years will see higher failure rates in the oldest portion of the fleet.

Using Backblaze Data for Drive Selection

Despite the limitations, Backblaze data provides the most reliable comparative signal available for drive selection:

For HDD selection: Compare models that appear in Backblaze's data with large sample sizes. A model consistently below 1% AFR in Backblaze's environment (e.g., Seagate Exos 12TB, WD Ultrastar DC HC520) is very likely more reliable than a model with 3–4% AFR in the same data. Apply a 1.5–2x multiplier to estimate likely rates in a desktop environment.

For SSD selection: Backblaze's SSD data does not cover most consumer SSDs. Use the enterprise data directionally (Samsung, Seagate, and WD enterprise SSDs appear reliable) and rely on manufacturer TBW ratings and independent review data for specific consumer model selection.

For NAS drive selection: The NAS-rated drives (WD Red Plus, Seagate IronWolf) are the consumer products closest to what Backblaze tests. Backblaze's data on similar enterprise models (WD Ultrastar, Seagate Exos) provides a reliability proxy for the NAS-tier products.

SMART Data vs. Backblaze AFR: Complementary Information

Backblaze AFR data tells you which drive models fail at what rates in aggregate. S.M.A.R.T. data tells you whether a specific drive in front of you is showing pre-failure indicators right now. Both are useful; they answer different questions:

AFR: Should I buy/use this drive model? (Population-level reliability) S.M.A.R.T.: Is this specific drive healthy? (Individual drive health)

For fleet management, both inform different decisions:

• Purchasing decisions: Use Backblaze AFR data to prefer reliable models
• Maintenance decisions: Use S.M.A.R.T. monitoring to identify individual drives approaching failure

GGFix monitors S.M.A.R.T. attributes on all connected drives, providing the individual drive health visibility that Backblaze population data cannot.

Frequently Asked Questions

Are Backblaze drives the same as drives you'd buy for a desktop PC?

No. Backblaze primarily uses enterprise-grade drives (Seagate Exos, WD Ultrastar, Toshiba MG series) that are not sold in retail consumer channels. The consumer-accessible NAS drives (WD Red, Seagate IronWolf) are the closest equivalents but are not identical products. Enterprise drives are typically manufactured to higher tolerances, with higher vibration resistance ratings and MTBF specifications than consumer drives.

How do I find Backblaze's current failure data?

Backblaze publishes quarterly failure reports on their blog at backblaze.com/blog. Reports are searchable by quarter, and Backblaze maintains a cumulative data set downloadable as a CSV. The blog posts present summarized findings; the raw data files allow custom analysis.

Does a low Backblaze AFR mean a drive is safe for mission-critical data?

Low AFR reduces risk but does not eliminate it. A 0.5% AFR means 1 in 200 drives will fail in a given year — if you have 200 drives, expect one failure annually. For mission-critical data, backup and redundancy are always required regardless of drive reliability ratings. Low AFR drives reduce the probability of needing the backup, not the need for the backup itself.

Is the WD Red (consumer NAS) significantly less reliable than the WD Ultrastar (enterprise) for business use?

In Backblaze's data, WD Ultrastar enterprise drives generally show lower AFR than consumer NAS equivalents, but both are more reliable than standard desktop drives. For small business NAS or PC fleet storage in moderate-use environments, WD Red Pro or Seagate IronWolf Pro are practical choices with good reliability profiles at consumer-accessible prices.

How should I use Backblaze data to plan SSD replacements in a fleet?

Backblaze SSD data provides directional guidance on brand/manufacturer reliability. For individual drive replacement planning, S.M.A.R.T. wear level is more actionable — replace drives when wear level exceeds 70–75%, regardless of the manufacturer's population-level failure rate data.