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8 Reasons Causing Reallocated Sector Count – And How to Fix it

Are you experiencing slow performance or strange noises from your hard drive? It could be due to reallocated sectors, which can cause data loss and corruption. In this article, we explore the eight most common causes of reallocated sectors and provide solutions to prevent or fix them. Learn how to monitor your hard drive errors, back up your data, and plan for a replacement after the useful lifespan of a hard drive.

Is your hard drive running slower than usual or producing strange noises? It’s possible that your hard drive is experiencing reallocated sectors, which are parts of the disk that can no longer be trusted to store data. Although reallocated sectors are a normal part of a hard drive’s operation, a consistent increase is a telltale sign of hard drive failure. To start monitoring your hard drive health, start your free trial of Hard Disk Sentinel.

In this article, we’ll explore the 8 most common causes of reallocated sectors and what you can do to prevent or fix them. We’ll also cover how to check your reallocated sector count and recommend a solution to help you monitor your hard drive errors, back up your data, and plan for a replacement after the useful lifespan of a hard drive. Keep reading to learn more!

What are reallocated sectors?

Reallocated sectors are parts of a hard drive’s platter that can no longer be trusted to safely store data. Each sector is quite small, holding just 512 bytes of data.

Here’s what happens:

  • When your hard drive encounters an error while reading, writing or verifying data, it marks the sector as bad.
  • It moves any data stored to a reserved area on the disk called spare sectors.
  • Then any further reads/writes targeting the bad sector automatically redirected to this spare area to prevent re-use of the original bad sector
  • This process of reallocation is done to prevent data loss and corruption.

Essentially, your hard drive has noticed a problem with a part of the disk. Instead of saving your data there, which is risky, it moves the data to a safe part of the disk and continues on with what it was doing.

The reallocated sector count can be an early warning sign of a failing hard drive, and increases in reallocated sectors are one of the telltale signs of a drive that’s dying. Reallocation is a normal part of a hard drive’s operation, but when the reallocated sector count continues to increase, it can slow down your drive by 10% or more. Worse, you may no longer be able to open files containing missing data. Unless you enjoy living dangerously, back up your data regularly and consider buying a new hard drive when the count becomes too high. For more signs of hard drive failure, check out this article.

There is no software or hardware fix to lower the reallocated sector count. If you attempt to open a hard drive to fix it, you could create more problems.

So why do these happen and why do you get a warning?

What are reallocated sectors

8 Reasons for Reallocated Sector Count Warning

If you’re experiencing issues with your hard drive, one possible cause could be reallocated sectors. There are several reasons why reallocated sectors may occur on a hard drive. In the following sections, we’ll explore eight potential causes of reallocated sectors and what you can do to prevent or fix them. So, if you want to learn more about how your hard drive works and how to keep it in good condition, keep reading!

Physical Damage to the Drive

Physical damage to the hard drive is one of the primary causes of bad sectors and reallocated sectors. It can happen due to a variety of reasons, such as dropping the drive, accidental impact, or natural disasters like floods or fires. Physical damage can cause significant harm to the internal components of the drive, such as platters or read/write heads, resulting in bad sectors. Unfortunately, if physical damage occurs, it is not repairable and often requires the hard drive to be replaced.

Mechanical Drive Issues

Mechanical drive issues, such as motor failure or read/write head failure, can cause bad sectors and reallocated sectors. The mechanical failure can happen due to various reasons, such as excessive usage, power surges, or mechanical stress. In some cases, mechanical issues may be repairable, but it requires professional data recovery services. If not repaired in a timely manner, the drive may continue to accrue bad sectors and may eventually become unusable.

SSDs don’t have the same problems, but can face other issues. Read our HDD vs SSD guide to learn more.

Mechanical drive issues


Overheating of the hard drive can also cause bad sectors and reallocated sectors. When a hard drive runs hot, it can cause damage to the internal components of the drive and increase the risk of sectors becoming bad. One of the primary reasons for overheating is a lack of proper ventilation, which can be caused by things like clogged air filters or a faulty cooling system. Overheating can be prevented by ensuring proper ventilation, and by limiting the use of the drive for long periods of time. For safe hard drive temps and how to monitor them, click here.

Forced Shutdowns Can Cause Data Corruption

When a computer is forced to shut down or experiences a sudden power loss, it can cause data corruption on the hard drive, even with modern hard drives. The sudden shutdown may interrupt the writing of a file and cause the data to become corrupted or locked. Possible connections between a forced shutdown and data corruption include unwritten HDD cache and interrupted disk updates. To prevent data corruption, it’s essential to ensure that the computer shuts down properly. If the issue persists, users should consider updating drivers or their computer’s BIOS.

Bad Sectors Cause Reallocation

The presence of bad sectors can also cause reallocated sectors. If the hard drive has existing bad sectors, the drive may be more prone to having additional sectors fail, resulting in reallocated sectors. The presence of bad sectors is not repairable, and users should replace the drive as soon as possible to prevent further data loss.

Bad Sectors Cause Reallocation

Intense Drive Usage for a Longer Duration

Intense drive usage for a longer duration can cause bad sectors and reallocated sectors. Heavy use can cause the drive’s internal components to wear out, leading to bad sectors. This can be prevented by limiting the use of the drive for long periods of time and allowing the drive to rest periodically.

Corrupt File

Corrupt files can cause bad sectors and reallocated sectors. If a file is corrupt, the drive may be unable to read it properly, causing damage to the sector. In most cases, the corrupt file can be deleted, and the sector can be marked as bad to prevent further issues.

Corrupt File

Aging Hardware Fails More Often

Just like an aging person, an aging hard drive can also become more prone to developing bad sectors and reallocated sectors. Over time, the drive’s internal components can wear out, and the magnetic surfaces of the platters can degrade, leading to read and write errors. This can cause sectors to go bad and eventually result in reallocated sectors. Unfortunately, aging hardware is not repairable, and the only solution is to replace the hard drive. 

If users notice a rise in their hard drive’s bad sector count, they should consider checking the drive’s age to determine if it’s the cause. As a general rule of thumb, hard drives that are over five years old are more likely to develop bad sectors and other issues. To prevent data loss, users should back up their data regularly and replace the drive when it’s reaching the end of its lifespan.

Aging Hardware Fails More Often

How to Check Your Reallocated Sector Count

Checking your reallocated sectors isn’t difficult, but you will need a specialist app. While there are several available, we recommend our own program, Hard Disk Sentinel. Let’s show you how to use the tool and then mention why we think it’s the best choice.

  1. Install and open Hard Disk Sentinel. On the Overview page, it immediately shows the amount of bad (reallocated) sectors on the drive. If you’re interested in the details:
  2. Open the S.M.A.R.T. view on the main nav tab.
  3. Search for the reallocated sectors count in the list.

Here’s what it looks like:

Reallocated sectors count SMART attribute

We recommend Hard Disk Sentinel because it gives users a clear overview of the necessary information about their drives. It can be used to test, back up, and protect hard drives. The result is a complete and thorough solution to help you check your hard drive health protect your data.

Fixing Reallocated Sectors

If your hard drive’s S.M.A.R.T. data shows an increased count of “ID 05 Reallocated Sector,” it’s a sign that your hard drive could be dying. Reallocated sectors are bad sectors that have been moved to another part of the disk, and there’s no way to fix them. If your data is important, make sure to back it up and consider buying a new hard drive. If your drive is still under warranty, you may be able to get a replacement, but don’t forget to back up your data first. Don’t panic, but take the backup seriously – it’s important for everyone.

If you want to try to repair your drive, read our full guide on how to fix a hard drive failure.

Should You Try CHKDSK Scan?

In short, no. CHKDSK was a great tool in the past. There are simply better options available now. CHKDSK is not useful for two reasons:

  1. There is no way to actually fix reallocated sectors. They are marked as bad and cannot be retrieved. This is good – as this way the original bad sectors are never re-used and can never risk data corruption / data loss.
  2. CHKDSK can actually put a lot of stress on your hard drive. It can produce excessive use and heavy read/write loads, which can lead to drive failure. If you want to learn more about CHKDSK on SSD check out our handy article.

Further, CHKDSK can actually damage an SSD. So, instead of running CHKDSK on SSD, use Hard Disk Sentinel instead.

Instead of CHKDSK, use Hard Disk Sentinel to monitor your hard drive, keep your data backed up, and help you know when it’s the right time to replace the drive.

Should You Try CHKDSK Scan

Returning A Drive With Reallocated Sectors

If your reallocated sector count is high and your drive is under warranty, then you could send it back for a replacement. Check your warranty documentation for specific times for a warranty and any exclusions. Before you send your hard drive away, back up your data! You will not receive the same hard drive back, so any data on yours will be lost.

Should You Use a Hard Drive with Reallocated Sectors?

Yes, it’s probably safe to continue to use a hard drive with few reallocated sectors. But, and this is a big but, reallocated sectors are a sign of data loss and/or storage capacity loss. You should view them as a serious warning to back up your data and plan for the replacement of your hard drive.


In conclusion, hard drive monitoring, backup, and planned replacement are essential for protecting your data and ensuring the longevity of your hardware. Reallocated sectors are an early warning sign of a failing hard drive, and the eight potential causes of reallocated sectors highlight the importance of regular monitoring and maintenance. Hard Disk Sentinel is the recommended solution for checking your reallocated sector count and for testing, backing up, and protecting your hard drive. Remember, there is no fix for reallocated sectors, so if your data is important, back it up regularly and consider buying a new hard drive. Don’t wait until it’s too late – take the necessary precautions to protect your data and hardware today.