Can bad sectors in HDD be repaired?

Quick Answers

Bad sectors on a hard disk drive (HDD) can sometimes be repaired, but not always. Here are some quick answers about repairing bad sectors:

  • Bad sectors occur when areas of the disk platter become physically damaged and data cannot be read or written reliably.
  • Low-level formatting tools can remap bad sectors to spare sectors set aside for this purpose. This repairs inaccessible bad sectors.
  • Bad sectors caused by physical damage cannot be repaired. These can only be identified and avoided using SMART monitoring tools.
  • It’s a good idea to backup data and replace drives that develop bad sectors. Relying on bad sector remapping is risky.
  • Scandisk and chkdsk can help identify bad sectors but cannot repair physical damage on the disk platters.

What Causes Bad Sectors?

Hard disk drives store data on quickly rotating circular platters inside the drive enclosure. These platters are coated with a magnetic film used to store data bits in the form of magnetic orientation.

Bad sectors occur when areas of the magnetic film become damaged or lose their ability to reliably store data. This can happen for a few different reasons:

  • Physical damage to the disk surface – For example, damage from a head crash or impact during operation.
  • Manufacturing defects – Imperfections in the physical disk platter media.
  • Wear and tear – Disk surfaces degrade over time, especially on drives with a lot of use.
  • Magnetization problems – Issues with the ability of the magnetic coating to be magnetized and retain data.

The end result is the same – spots on the physical disk platters that are flawed and unreliable for storing data. The drive will detect when writes fail or data cannot be successfully read from these areas.

How Do Drives Handle Bad Sectors?

Modern hard drives have techniques for working around bad sectors when they develop:

Spare sectors – Drives reserve extra sectors that are set aside for remapping purposes if needed. If the drive detects a bad sector, it will remap it to use a spare sector instead. This is done automatically and transparently.

S.M.A.R.T. monitoring – The drive constantly monitors for read/write errors and problems accessing data. It logs these errors and can give warnings if issues are detected.

Bad sector mapping – If a sector goes bad, the drive logs its physical location so it can avoid storing data there in the future. The sector is essentially quarantined.

These techniques allow the drive to keep functioning smoothly even if some sectors go bad. However, the ability to remap bad sectors is limited. If too many develop, the drive will eventually run out of spares and be unable to remap new bad sectors. At that point, data loss is likely.

Can Bad Sectors Be Repaired?

It depends on the specific cause and nature of the bad sector. Here are the general possibilities:

Remappable sectors can be repaired – If the drive detects an inaccessible sector, it can remap to a spare. This “repairs” the bad sector and masks the problem.

Physical damage cannot be repaired – A bad sector caused by physical damage to the disk platter can’t be fixed. The damaged area persists.

Refreshes can help some bad sectors – Sometimes bad sectors are unstable and can work temporarily. Rewrites and surface refreshes can help these areas.

Manufacturer defects cannot be repaired – Bad sectors existing since manufacturing time typically cannot be fixed. These are permanent.

So in summary, bad sectors caused by physical damage cannot be repaired. But sectors going bad due to other reasons have a chance of being remapped or temporarily refreshed into working.

Can Low-Level Formatting Fix Bad Sectors?

Low-level formatting tools for hard drives work by:

  1. Locating all defective sectors.
  2. Remapping those sectors to use spare sectors.
  3. Freeing up all other sectors to be used by the filesystem.

This process essentially isolating all the bad areas, then only exposing good sectors to the operating system. This can repair bad sectors as far as the OS is concerned.

However, physical damage is not actually fixed. Any bad sectors caused by platters flaws or damage will still exist. The drive will eventually run out of spare sectors and have no fallbacks.

So low-level formatting hides bad sectors rather than fixing them. This means the issues may reappear later. It’s advised to still replace drives that develop a high number of bad sectors even if formatting seems to fix it.

Can Scandisk or chkdsk Repair Bad Sectors?

Tools like Scandisk and chkdsk are designed to scan for filesystem errors and inconsistencies – not physical bad sectors.

Running these tools can identify bad sector locations by detecting areas that trigger read or write errors. However, they have no capability to actually repair those bad sectors themselves.

The utility may report the bad sector locations back to the operating system so they can be quarantined and avoided. But the physical media will remain damaged.

So while scandisk or chkdsk can help identify bad sector problems, they cannot resolve the physical issues that cause sectors to go bad. Their repair abilities are limited to file and directory errors only.

Can Spinrite Repair Bad Sectors?

Spinrite is a utility that claims to be able to repair bad sectors in some cases. It works by repeatedly reading, rescanning, and rewriting to troublesome areas of the disk.

This can sometimes refresh unstable sectors and allow them to operate again, temporarily. However, Spinrite cannot fix sectors damaged due to physical defects or platter damage. The physical flaws remain.

So Spinrite may be able to revive some volatile bad sectors, but cannot fix permanent ones from physical damage. As with low-level formatting, consider replacing a drive with recurring bad sectors even if Spinrite appears to fix it.

Can Restoring Magnetism Fix Bad Sectors?

In theory, bad sectors caused by magnetization issues on the disk platters could be repaired by re-magnetizing the media. Tools exist that claim to help restore magnetism.

However, there is little evidence that such tools are effective when physical damage has occurred. The scope for correcting bad sectors by restoration of magnetism appears to be small.

Most often, bad sectors are caused by physical damage to the disk surface or are present since manufacturing. These types of bad sectors cannot be fixed by remagnetization.

Can Firmware Updates or HDD Regenerators Fix Bad Sectors?

Tools such as HDD Regenerator claim to repair bad sectors by re-writing the disk platters at a lower level than the formatting process.

However, they still cannot physically fix or overwrite sectors with failed platter media. A regenerator cannot make a damaged disk surface pristine again.

Firmware updates typically do not address bad sectors. The purpose of drive firmware is to add features or fix logic bugs in the drive’s operation. Firmware allows remapping bad sectors but does not attempt to repair them.

So neither firmware updates nor drive generators are an effective solution for physical bad sectors. The media damage remains. The best solution is still to replace the drive.

Signs That a Hard Drive Has Bad Sectors

Here are some symptoms that indicate a hard drive may have bad sectors:

  • The operating system reports read/write errors happening at the hardware level.
  • Difficulty reading or writing data, or corrupted data. Particularly if it happens in consistent areas.
  • The hard drive makes unusual clicking or grinding noises during operation.
  • Files and folders that can’t be opened or suddenly become corrupted.
  • S.M.A.R.T. errors show up indicating hardware problems on the drive.
  • The BIOS reports unusable sectors during system startup.

If multiple bad sectors start to develop, the operating system may have trouble writing new files as it tries to avoid the bad areas. Performance will degrade significantly.

Should You Keep Using a Drive with Bad Sectors?

It’s not recommended to continue relying on a hard drive once a substantial number of bad sectors develop. Here’s why:

  • Bad sectors indicate the physical media is degrading or damaged.
  • Problems will likely continue to get worse with more bad sectors.
  • The drive has limited spare sector fallbacks before total failure.
  • Eventual data loss is likely as the bad areas spread.
  • Performance will get progressively worse as more sectors fail.

For critical data or high use drives, it’s wise to replace the unit at the first signs of bad sectors before catastrophic failure.

How Can Bad Sectors Be Prevented or Avoided?

While bad sectors cannot always be prevented, there are ways to lower the risks:

  • Use S.M.A.R.T. tools to monitor drive health and detect problems early.
  • Maintain a reasonable workload level for each drive rather than overworking it.
  • Keep drives properly cooled and in stable environments.
  • Minimize physical impacts, drops, vibrations that can stress and damage drives.
  • Perform regular backups so drive failures and bad sectors have less impact.

Carefully monitoring health metrics, avoiding stress, and planning ahead are the best protections against bad sector problems.


Bad disk sectors are an inevitable fact of life for aging hard drives. While tools exist to help identify, isolate, remap, or refresh bad sectors, the physical damage cannot actually be repaired in most cases.

Low-level formatting and software utilities may seem to fix bad sectors, but the issues frequently reoccur. The only true solutions are replacing the drive or using backups to work around the problem areas.

Carefully monitoring your drives with S.M.A.R.T., avoiding undue stressors, and planning redundancy will help maximize the healthy lifespan of a hard drive. But inevitably, physical degradation will take a toll over time leading to bad sectors.