Hard disk drives (HDDs) are a common type of storage device used in computers. They store data on spinning magnetic disks called platters. While HDDs have become very reliable over the years, they can and do still fail from time to time.
What is the average failure rate for HDDs?
Studies have shown that most HDDs have an annual failure rate between 2-10%. Consumer-grade HDDs tend to be on the higher end, around 10% per year. Enterprise and server-grade drives are engineered for better reliability and lower failure rates, more in the 2-4% range.
To put some numbers on it:
| Drive Type | Annual Failure Rate |
| Consumer HDD | 10% |
| Enterprise HDD | 2-4% |
So if you have 10 consumer HDDs, you could expect 1 failure per year on average. Enterprise drives would see a failure every 2-5 years for 10 drives.
What causes HDDs to fail?
There are a number of factors that contribute to HDD failure:
- Mechanical failure – The spinning disks and internal components wear out over time and can eventually fail. HDDs have moving parts and mechanics that are subject to failure.
- Bad sectors – Also known as media errors. Flaws develop on the magnetic disks that cause sectors to become unusable for storing data. These bad sectors spread over time.
- Fragmentation – When files get fragmented across the disk, the HDD has to work harder to piece the files back together, wearing it out faster.
- Electronic components – The electronic boards, chips and other components that control the HDD can also fail even if the mechanical parts are fine.
- Heat – Excessive heat can damage HDD components and increase the rate of failure.
- Vibration – HDDs are sensitive to vibration which can damage internal parts over time.
How does drive age affect failure rates?
In general, the rate of HDD failure increases with age as components slowly degrade over time. Here is how annualized failure rate typically increases with age:
| HDD Age | Annual Failure Rate |
| 0-1 years | 2-5% |
| 2-3 years | 5-10% |
| 4-5 years | 10-15% |
| 6-10 years | 15-20% |
Brand new HDDs often have failure rates around 2-5%. By 4-5 years, failure rates typically increase to 10-15%. At 6-10 years of age, HDD annual failure rates are usually in the 15-20% range.
Of course, these rates are averages across many drives. Individual results can vary. Some drives fail right away while others last beyond 10 years. But in general, the older a drive gets, the more likely it is to fail.
Do SMART stats indicate if a drive is about to fail?
Self-Monitoring, Analysis and Reporting Technology (SMART) provides statistics on the internal operation and health of a HDD. Some key SMART attributes related to failures include:
- Reallocated sectors – The number of bad sectors that have been replaced by spare good sectors.
- Seek errors – Errors encountered while mechanically moving the HDD heads.
- Spin retries – Failed attempts to spin up the platters.
- Temperature – Current internal temperature.
- Pending sectors – Sectors that have read errors and are likely to become bad sectors.
Sudden increases in reallocated or pending sectors often indicate a drive is having issues and may fail soon. High or rising temperatures can also accelerate failure. Seek errors point to mechanical problems. And spin retries mean the motor is struggling.
However, some drives fail suddenly without any prior SMART indications. And some slowly deteriorating drives can last for years. So while SMART stats are useful, they don’t provide a foolproof prediction of impending failure.
Does the warranty period indicate expected drive life?
HDD warranties typically range from 1-5 years for consumer models. Enterprise and server drives often have 3-5 year warranties. The longer 5 year warranties found on some drives seem to imply an estimated functional life of around 5 years.
However, there are a few caveats to consider:
- Warranties cover manufacturing defects, not age-related failures. Many drives last beyond the warranty period.
- Lengthier warranties are used partly as a marketing tactic.
- Heavy use can wear out a drive before the warranty expires.
- The warranty only guarantees a replacement if the drive fails, not continued life beyond the warranty.
So while longer warranties suggest the manufacturer has confidence in the drive’s reliability, it’s not a guarantee that the drive will actually last that long in practice.
Does the manufacturer or model affect failure rates?
Failure rates do vary between HDD manufacturers and models. Studies have shown certain brands and models to be more or less reliable than others. For example, Backblaze analyzed drive failure rates amongst different models and found:
| Manufacturer | Annual Failure Rate |
| HGST | 1.1% |
| Western Digital | 2.8% |
| Seagate | 5.1% |
So HGST drives had the lowest failure rates. Seagate had the highest. Of course, model-specific engineering and components also affect reliability.
Enterprise drives from the same manufacturer tend to have lower failure rates than consumer models. So the intended market segment factors into reliability as well.
How does workload affect HDD failure rate?
Workload, or the amount of usage a HDD sees, can influence failure rates:
- Low workload – Drives used infrequently as cold storage may have very low failure rates, lasting many years.
- Standard workload – Average everyday desktop/laptop use for things like documents, media, apps, etc. falls in the normal failure rate ranges.
- High workload – Drives used heavily for things like servers or video editing wear out quicker and have higher failure rates.
Drives worked hard every day tend to fail faster. Lightly used drives last longer. Power-on hours tracked by SMART stats give an indication of workload.
Are refurbished or used HDDs more likely to fail?
Refurbished and used HDDs generally have higher failure rates than new drives:
- Refurbs may not have been thoroughly checked or repaired.
- Used drives have accumulated wear from past use.
- Failure prone drives often get resold rather than scrapped.
- No factory testing and quality control.
- Shorter remaining usable lifespan.
Failure rates for refurbished HDDs can be 20-30% higher than new drives. And used HDDs over 3 years old often see failure rates upwards of 15-25% per year.
New HDDs with full factory warranties are the most reliable option. Heavily used drives sold “as-is” with no warranty tend to be risky.
Are cheaper low-end HDDs more prone to failure?
There is a general correlation between lower HDD prices and higher failure rates:
- More expensive drives use higher quality components and engineering.
- Server and NAS drives designed for reliability and uptime cost more.
- Cheap bargain HDDs cut costs resulting in reduced longevity.
- Lower-end consumer drives prioritize capacity over reliability.
That said, a higher price doesn’t guarantee reliability. Some expensive models still have high failure rates. And a good deal on a high-quality drive can provide both low cost and good longevity.
As a rule of thumb however, the cheapest drives tend to not last as long. Paying a little more for an established quality model is advisable for more critical applications.
Do SSDs have a lower failure rate than HDDs?
Solid State Drives (SSDs) based on flash memory technology have much lower failure rates than mechanical hard disk drives:
- No moving parts susceptible to wear and tear
- More shock and vibration resistance
- Cooler operating temperatures
- Faster read/write speeds reduce wear from drive operations
Typical SSD annual failure rates are around 0.5-2%. High-end enterprise SSDs can be even lower, with rates as low as 0.2%. That’s up to 10x lower than HDD failure rates.
However, SSDs have limitations like finite write endurance. HDDs are still preferred for frequently rewritten data and archival storage due to lower long-term costs.
Conclusion
Most hard disk drives have an annual failure rate in the 2-10% range, with higher rates as the drives age beyond 3-5 years. Enterprise and server-grade models engineered for reliability have markedly lower failure rates around 2-4%. Workload, manufacturer quality, model differences, wear and tear, and other factors can all influence HDD failure rates.
Regular backups of important data are recommended to mitigate the impact of inevitable HDD failures. RAID redundancy can also improve resilience. And solid state drives provide much lower failure rates for more critical data, albeit at a higher cost.