How likely is it for an external hard drive to fail?

External hard drives are convenient storage devices that allow you to easily expand the storage capacity of your computer. However, like any electronic device, external hard drives can and do fail. In this article, we will examine the factors that contribute to external hard drive failure and provide estimates on failure rates based on various statistics and studies.

What causes external hard drives to fail?

There are several potential causes of external hard drive failure:

  • Mechanical failure – The physical components of the hard drive, such as the read/write heads, motor, and platters, can wear out and fail over time.
  • Logical/firmware corruption – Errors in the hard drive’s firmware or file system can prevent it from being recognized or data from being accessed.
  • Impact damage – Physical impacts, drops, bumps, etc. can damage the drive.
  • Overheating – Excessive heat can damage components and increase failure rates.
  • Electrical issues – Power surges, static electricity, wiring issues can fry the drive’s circuitry.
  • Manufacturing defects – Imperfections in the production process can lead to premature failure.

Most external hard drive failures are caused by mechanical failure or component wear over time. The more a drive is used, the higher the likelihood of failure. Environmental factors like heat, physical shocks, electricity problems also raise the chance of failure.

What is the average lifespan of an external hard drive?

There are no definitive figures on exactly how long external hard drives last on average. However, looking at various statistics and manufacturer estimates, we can come up with a reasonable lifespan estimate:

  • Most manufacturers offer 1-3 year warranties on external hard drives, suggesting they should function for at least this long under normal use.
  • 90% of hard drives survive for 3 years based on a study by Backblaze of over 25,000 consumer-grade drives.
  • Less than 50% of hard drives survive past 6 years.
  • Hard drives kept in ideal conditions may last 4-5 years on average.
  • Drives that receive frequent use and travel are prone to earlier failure.

Based on this data, we can estimate that on average, most external hard drives can be expected to last between 3-5 years under normal use before mechanical failure becomes likely.

What is the annual failure rate for external hard drives?

Failure rate statistics for external hard drives vary across different studies, but generally fall somewhere in the range of 2-10% per year, after the first 1-2 years of use. Here are some reported annualized failure rates:

  • Backblaze: About 2% failure rate per year for drives 1.5-2 years old.
  • Online Tech Tips: Estimates 3-5% annual failure rate for external HDDs.
  • SquareTrade: Found nearly 10% early failure rate for some Seagate external models.
  • Principled Technologies: Measured a 7.5% annual failure rate across various consumer-grade external HDDs.

These studies indicate that on average, an annual failure rate of around 2-5% per year can be expected once an external hard drive is 1-2 years old, with higher failure rates in the 5-10% range certainly possible as well.

Does brand/model affect failure rate?

While all hard drives are prone to failure over time, some brands and models do tend to perform better than others based on various studies:

  • Backblaze found Hitachi drives to be most reliable, followed by Western Digital.
  • Another Backblaze study found high failure rates among some Seagate external models.
  • HGST (owned by Western Digital) scores well on reliability in multiple reports.
  • Western Digital My Passport drives had the lowest failure rates in one study.
  • Higher-end enterprise-class drives often last longer than consumer-grade drives.

While no hard drive is immune from failure, paying more for drives from reliable brands like Hitachi, Western Digital, or HGST can improve your chances of getting a longer-lasting external hard drive.

Do SSDs fail less than HDDs?

External solid state drives (SSDs) do tend to have lower failure rates and longer average lifespans than traditional rotational hard disk drives (HDDs). Here are some advantages of external SSDs:

  • No moving parts susceptible to mechanical failure.
  • Estimated 2.0% annual failure rate, compared to 2-5% for HDDs.
  • Less prone to damage from drops, vibration, fragmentation.
  • Estimated 5-7 year average lifespan vs. 3-5 years for HDDs.

However, SSDs have downsides like lower capacities and higher prices compared to HDDs. Overall, SSDs have proven to be more reliable and durable than HDDs, but have higher upfront costs.

Does the interface (USB, eSATA, etc.) affect reliability?

The data interface used by an external hard drive does not seem to have a major effect on the drive’s inherent reliability. However, some interfaces like eSATA provide advantages:

  • USB: Simple plug-and-play, but may be slower than other interfaces.
  • FireWire: Fast transfer speeds, but not as widely supported.
  • eSATA: Provides fast SATA speeds externally; more reliable than USB.
  • Thunderbolt: Very fast interface, with daisy chaining capability.

The interface itself does not make a drive more prone to failure. However, interfaces like eSATA and Thunderbolt offer more reliable connectivity and better performance compared to USB, which can reduce transfer errors.

Do higher storage capacity drives fail faster?

Some studies have found a weak correlation between higher storage capacity hard drives and higher failure rates. Platter density increases are likely contributing factors. However, the differences are fairly small:

  • Backblaze: 1.5-2x higher failure rates for high capacity (6TB+) vs. low capacity drives.
  • Backblaze: 4TB drives actually failed less than 2TB and 3TB models.
  • Principled Technologies: No strong correlation between capacity and failure rate.

In general, very high capacity external hard drives have at most a moderately higher failure rate compared to lower capacity models. Capacity alone should not be a major consideration for reliability.

Are enterprise or NAS drives more reliable?

Enterprise-class and NAS hard drives designed for 24/7 operation in servers and data centers do offer better reliability than consumer-grade desktop drives in some respects:

  • Higher workload tolerance, better components – bearings, electronics, etc.
  • Designed for constant operation rather than intermittent use.
  • Often longer warranties – 5 years vs. 2-3 years for consumer models.
  • Some additional features like TLER for RAID recovery.

However, these advantages come at a significantly higher cost. Overall, enterprise and NAS drives are better options for frequently accessed storage and mission-critical data, but consumer drives offer sufficient reliability for less demanding home/office use.

What environmental factors increase failure rate?

Environmental factors definitely influence the lifespan of external hard drives. Some factors that can accelerate failure:

  • Heat: Drives exposed to high temperatures fail faster.
  • Vibration: Shaking from travel or impacts can damage drives.
  • Humidity: Very damp/humid environments can corrode electronics.
  • Dust: Can accumulate and cause overheating and mechanical issues.
  • Air pressure: Very high altitudes increase failure rates.

Ideally, external hard drives should be kept in clean, climate-controlled environments away from vibration, extreme temperatures, and rapid air pressure changes.

How does drive usage and idleness affect failure rates?

Regularly accessing and writing data to an external hard drive does seem to increase the likelihood of failure compared to very infrequent drive usage:

  • Heavily used drives fail faster due to more wear on moving parts.
  • Drives powered on 24/7 tend to fail faster than intermittently used ones.
  • However, very long periods of idleness also raise failure risk due to seized bearings.

The “sweet spot” for minimal failure risk seems to be daily/weekly drive use with powering off the drive during extended idle times. Finding the right balance can maximize an external drive’s lifespan.

Can sudden failure be predicted and prevented?

Advanced warnings of imminent drive failure are difficult, but some signs include:

  • Increasing bad sectors and recovered errors.
  • Frequent bad block reallocations.
  • Slow performance, long read/write times.
  • Clicking, beeping or other odd noises.
  • Filesystem corruption, frequent crashes.

Monitoring a drive’s SMART stats can provide early warning of problems developing. However, outright failure is still often abrupt and unpredictable. The best defense is comprehensive backups to reduce data loss risk.

How crucial is an external hard drive’s warranty period?

The warranty coverage for an external hard drive does give some important guarantees and protections:

  • Warranties usually range from 1-5 years for external storage.
  • Replacement of defective drives due to manufacturing flaws.
  • Potential data recovery services if drive is still under warranty.
  • Typically required for manufacturer RMAs and replacements.

Larger warranty coverage of 3-5 years provides more protection from early failures. But mechanical failure past the warranty period is still very possible, making backups essential.

What backup measures should be taken to mitigate data loss?

To protect against failure of an external hard drive, some essential backup strategies include:

  • Regularly backing up important data to a second external drive.
  • Offsite “cold storage” backups to guard against disasters like fires, floods.
  • Using cloud storage for automated, remote backups.
  • Ensuring backups occur before drive reformats or OS reinstalls.
  • Occasional drive cloning to simplify backup drive replacement.

No single backup method is sufficient by itself. Using multiple redundant backup techniques is ideal for minimizing the risk of unrecoverable data loss due to external drive failure.

How can external hard drives be protected when traveling and moving?

To maximize the lifespan of portable external hard drives, some precautions include:

  • Use carrying cases or padded pouches designed for external storage.
  • Avoid tossing or dropping drives or exposing them to physical shock.
  • Disconnect and eject the drive safely before transit.
  • If possible, remove drives before packing/moving computers.
  • Avoid exposing drives to major temperature/humidity changes.
  • Allow time for drives to acclimate before powering on after transports.

Exercising caution when moving or traveling with external hard drives can prevent many accidents that would otherwise damage drives and contribute to earlier failure.

Should obsolete or damaged drives be replaced proactively?

While functional hard drives can often endure for years, some signs that proactive replacement may be worthwhile include:

  • Outdated interfaces like USB 1.0/2.0 or FireWire 400/800.
  • Very old drives with more than 5 years of moderate use.
  • Any evidence of chassis damage or physical shocks.
  • Assembly difficulties, loose cables, worrying noises.
  • persistently slow performance and long access times.
  • Heavy bad sector counts and I/O error rates.

Upgrading to a newer, faster external drive periodically can sidestep issues before failure strands data on deteriorating drives.


In summary, while average failure rates for external hard drives are relatively low, all drives will eventually fail given enough time and use. To maximize the lifespan of external storage, treat drives gently, maintain proper operating conditions, and retire older units proactively. Most importantly, diligent backups to redundant external and cloud storage ensures that data loss is minimized when failure does occur.