What happens when a HDD fails?

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What happens when a HDD fails

Quick answers

When a hard disk drive (HDD) fails, the data stored on it becomes inaccessible. The most common failure modes for HDDs are electronic failures, head crashes, and firmware corruption. Mechanical failures can also occur. When an HDD fails, important data may be lost permanently if no backups exist. However, data recovery services may be able to recover some or all of the data depending on the nature of the failure.

What is a hard disk drive (HDD)?

A hard disk drive (HDD) is a non-volatile data storage device used in computers and other devices. It uses rotating magnetic platters to store data magnetically. HDDs come in different form factors and capacities. Common HDD sizes today are 3.5″ and 2.5″ while common capacities range from 500GB to 10TB for consumer drives.

The primary components of an HDD include:

  • Platters – Aluminum or glass disks that data is written to. Platters are coated with a magnetic recording material.
  • Read/write heads – Devices that magnetize and sense the magnetic fields on the platters to read and write data.
  • Spindle motor – Spins the platters at high speeds, typically 5400 to 15,000 RPM.
  • Actuator arm – Moves the heads across the platters.
  • Firmware – Low-level software that provides the interface between the HDD electronics and operating system.
  • Controller board – Circuit board with the electronics that control the HDD.

What causes HDDs to fail?

There are several main failure modes that can occur with HDDs:

Electronic failures

The electronics in the HDD can fail leading to the drive malfunctioning or becoming unresponsive. This includes failures of components like the controller board, motor driver, or logic chips. If the HDD’s controller fails completely, the drive will not be detected by the computer at all.

Head crashes

A head crash refers to the read/write head physically impacting or scraping the platter surface. This usually gouges the platter and can destroy data in the area where the head crashed. Head crashes most often occur due to:

  • Shock impact during operation
  • Wear and tear over time degrading the head suspension
  • Contamination getting stuck on the head
  • Platter surface defects

Head crashes tend to get worse over time. Once one head crashes, other heads may start failing as particles from the crash spread.

Firmware corruption

The firmware on the HDD can become corrupted or damaged. This can happen due to:

  • Faulty firmware updates
  • Power surges
  • Electrical static discharge
  • Corruption of low-level sectors where firmware code resides

Corrupted firmware can lead to the HDD acting erratically or becoming undetectable by the operating system.

Mechanical failures

Less common mechanical failures include:

  • Spindle motor failure – If the platter motor fails, the platters stop spinning causing the heads to lose alignment and the drive to become inoperable.
  • Bearing wear – Bearings allow the spindle and actuator arm to rotate smoothly. If bearings wear out, the drive may make grinding noises and eventually seize up.
  • Failed actuator arm – Responsible for moving the heads. If it fails, heads cannot access data.
  • Degraded lubricant – Lubricant is used to reduce friction. If it breaks down, can lead to increased wear on mechanical parts.

How does data get corrupted or lost when a HDD fails?

Data loss or corruption can occur through different mechanisms depending on the failure mode:

  • Electronic failure – Can cause data currently being written to platter to be lost or garbled. However, data already written is generally intact unless heads start crashing as well.
  • Head crash – Physically destroys data in path of crash on platter. Adjacent data also at risk. Heads bouncing can corrupt data.
  • Firmware corruption – May make existing data on drive inaccessible. Can also result in corrupt or incomplete writes.
  • Mechanical seizure – Heads get stuck in place so data cannot be read. Platters stop spinning so active writes may be lost.

To summarize, electronic failures tend to affect new writes while physical damage and firmware issues put existing data at risk.

Can failed HDDs be repaired?

In some cases failed HDDs can be repaired, but this depends on the failure mode and extent of damage. Here are some examples:

  • Electronics replacement – If electronics like controller board have failed, drive may work by replacing those parts.
  • Head replacement – Individual failed heads can be replaced if damage is limited.
  • Firmware reprogramming – Corrupted firmware can be restored if hardware is functional.
  • Motor or arm replacement – Mechanical repairs possible but expensive.

However, there are limits to HDD repair viability:

  • Extensive physical damage to platters cannot be repaired.
  • Older model HDDs may not have replacement parts available.
  • Repair costs quickly become comparable to new drive costs.
  • No guarantee repaired drive will have extended lifetime.

So while some failed HDDs can be repaired, replacement is often a more cost effective option if the failure is severe or physical in nature.

Is data recovery possible from failed HDDs?

Data recovery specialists are often able to recover some or all data from failed HDDs depending on the failure mode. Here are some common recovery scenarios:

  • Electronics failures – Data usually fully recoverable if no physical damage has occurred yet.
  • Minor head crashes – Data likely recoverable except in small number of sectors damaged.
  • Firmware issues – Data recovery depends on extent of corruption. Full recovery may be possible.
  • Motor seizures – Data typically fully recoverable if no physical damage.

However, extensive physical damage presents challenges for recovery:

  • Severe head crashes destroy data in large areas of platters. This data is unrecoverable.
  • Platter damage from shock or scraping can also cause permanent data loss.
  • Failed read/write heads may prevent accessing data.

So while basic electronic failures and firmware issues are very recoverable, severe physical damage ultimately determines how much data can be salvaged from the drive.

Can lost data be recovered after HDD format or repartition?

When an HDD is formatted or repartitioned, the file system metadata is erased and rebuilt. However, the existing data on the drive platters is unchanged. So data recovery is often possible:

  • Data recovery software can scan drive platters and rebuild file system information.
  • This allows recovering original folders and file names.
  • Recovery success depends on extent of platter overwrite after format.
  • More overwrite makes recovery harder but success still possible.

Some caveats to data recovery after format or repartition:

  • Fully rewriting entire drive with zeros makes recovery near impossible.
  • Data fragments may be recovered but original file names lost.
  • OS reinstall typically involves more complete reformatting.
  • Encrypted volumes hamper recovery without decryption key.

So while recovering data from a quick format or repartition is very possible, more extensive drive erasure or rewriting does complicate data recovery.

Best practices for preventing HDD failure

You can help avoid premature HDD failure by following best practices:

  • Handle drives gently – Physical shock is major cause of failure. Avoid drops, bumps.
  • Maintain stable temperature – Excessive heat causes failures. Ensure good airflow.
  • Keep clean – Dust buildup retains heat. Don’t smoke near drives.
  • Use surge protectors – Guards against power spikes damaging electronics.
  • Do not move during activity – Can cause head crashes and damage.
  • Perform regular backups – Critical for minimizing data loss when failures occur.

Following best practices reduces the chances of HDD failure. But failures will still eventually occur due to mechanical wear over time. So backups are always essential.

How to recover data from failed or damaged HDDs

If your HDD has failed and you need to recover data from it, here are some steps to take:

  1. Stop using the drive immediately if you notice signs of failure.
  2. Determine failure symptoms – strange noises, not detected, corrupted data, etc.
  3. Evaluate if DIY recovery is possible using software tools.
  4. If not, consult a professional data recovery service.
  5. If heads have crashed, do not attempt to run drive and risk further damage.
  6. Ask recovery company about likely success rate for your drive failure type.
  7. Understand that severe physical damage may make data unrecoverable.
  8. Follow recommendations from recovery team on handling of failed drive.
  9. For best results, retain both failed drive and recovered data.

As a last resort, recovery companies may attempt invasive physical repair of drives. But this has considerable cost and risks.

Choosing a data recovery service

Key factors to consider when choosing a data recovery service:

  • Experience with your specific HDD failure type
  • Capabilities – Class 100 cleanroom, platter imaging, spare parts
  • Security practices – data protection guarantees
  • Cost structure – free evaluations, flat fees, price per recoverable GB
  • Reputation based on independent reviews
  • Successful recovery rate
  • Return shipping insurance options

Avoid companies making unrealistic guarantees or that require significant payment upfront. Seek firms specializing in HDD recovery with a proven track record.

Preventing data loss when HDDs fail

Since HDD failures are inevitable, following a robust backup strategy is key to avoiding major data loss when they occur. Recommended approaches include:

  • Maintaining at least 3 copies of important data (live drive, local backup, cloud/offsite backup).
  • Using redundant storage like RAID arrays to limit impact of single drive failures.
  • Backing up regularly – at least weekly if not daily for critical data.
  • Storing backups offline and offsite to protect from physical disasters.
  • Testing backups regularly to verify recoverability.
  • Backing up entire drive images, not just individual files.
  • Using versioning so older versions of files can be recovered.

No backup method is foolproof. But combining multiple backup types and frequencies substantially limits the extent of data loss from inevitable HDD failures.

Conclusion

HDDs fail frequently due to factors like mechanical wear, physical damage, and electronic faults. Failure can lead to partial or complete data loss depending on the fault type and severity. While data recovery from failed drives is possible, extensive physical damage ultimately limits what can be salvaged. To minimize risk, combining drive best practices with a robust backup strategy offers the best protection against data loss when HDD failure occurs.