Repair bad blocks on hard drive

Hard drives are vital for storing personal, professional, and system-critical data. But as durable as they may seem, these devices are not immune to damage, especially in the form of bad blocks. Over time, a hard drive may develop bad sectors that can interfere with data integrity, lead to frequent crashes, or even result in permanent data loss. Understanding and repairing bad blocks is a crucial step in extending your drive’s lifespan and preserving your files.

What Are Bad Blocks on a Hard Drive?

A bad block (or bad sector) is a sector on a hard disk that cannot be read or written to due to physical damage or logical corruption. Each block on a hard drive holds a fixed amount of data (typically 512 bytes or 4096 bytes), and when one of these blocks becomes unreadable, it’s flagged as “bad.”

Types of Bad Blocks

Physical (Hard) Bad Blocks

Caused by physical damage: wear and tear, manufacturing defects, or dust particles

Permanent and cannot be fixed

Must be isolated using disk repair utilities

Logical (Soft) Bad Blocks

Result from software errors, sudden shutdowns, or power failures

Can often be repaired using scanning and error-checking tools

Common Symptoms of Bad Blocks

Detecting bad blocks early can help avoid catastrophic data loss. Here are the typical signs:

Files taking unusually long to open or copy

Frequent system crashes or freezes

Errors like “Cyclic Redundancy Check (CRC)”

File corruption or unreadable files

Boot errors such as “Operating System Not Found”

S.M.A.R.T. warnings from monitoring software

Strange clicking sounds from the hard drive (indicates physical damage)

What Causes Bad Blocks?

Understanding the root cause can help prevent further damage.

Age and wear: Older drives naturally accumulate bad sectors

Power surges or outages: Sudden loss of power can corrupt blocks

Overheating: Drives used in poorly ventilated environments degrade faster

Physical shocks: Dropping a laptop or external drive may create bad blocks

Manufacturing defects: Some sectors may be flawed from the start

Virus or malware: Rarely, malicious software can cause data corruption at the block level

How to Detect Bad Blocks

There are multiple ways to check for bad sectors. Some involve using built-in system tools, while others require third-party software.

1. Windows CHKDSK Tool

The Check Disk utility in Windows can scan your hard drive for errors.

Steps:

Press Windows + X → click Command Prompt (Admin)

Type the command:

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chkdsk C: /f /r /x

/f: Fixes errors on the disk

/r: Locates bad sectors and recovers readable info

/x: Forces dismount of the volume before scan

Restart your computer if needed. CHKDSK will scan and attempt repairs.

2. Disk Management & Event Viewer

Open Disk Management to see if your drive is marked as “Healthy.” Then:

Press Windows + X → Event Viewer

Navigate to:

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Windows Logs → Application → Filter by “Wininit”

This displays CHKDSK results after a reboot

3. SMART Monitoring Tools

S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) provides health info.

Recommended tools:

CrystalDiskInfo

GSmartControl

Hard Disk Sentinel

Look for attributes like:

Reallocated Sector Count

Current Pending Sector Count

Uncorrectable Sector Count

If values are high or marked in yellow/red, your drive is deteriorating.

How to Repair Bad Blocks

The repair method depends on whether you are dealing with logical or physical bad sectors.

A. Repair Logical Bad Blocks

Logical issues can usually be fixed using software-based tools. These include both native OS tools and third-party programs.

1. Using CHKDSK (Windows)

As covered earlier, CHKDSK with /r will scan and recover info from bad sectors.

Note: CHKDSK cannot fix physically damaged sectors but will mark them as unusable.

2. Mac Disk Utility (macOS)

Steps:

Open Disk Utility

Select the drive → click First Aid

Click Run to scan and repair

3. FSCK (Linux)

Steps:

Open terminal and unmount the drive:

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sudo umount /dev/sdX1

Run fsck:

bash

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sudo fsck -cfv /dev/sdX1

-c: Check for bad sectors

-f: Force check

-v: Verbose output

B. Isolate or Repair Physical Bad Blocks

Physical sectors can’t be repaired, but they can be isolated to prevent system access.

1. HDD Regenerator (Windows)

Scans for bad sectors

Attempts magnetic realignment (limited success)

Good for older drives

2. Victoria HDD (Windows)

Advanced diagnostics and surface tests

Can scan sector by sector and remap damaged areas

3. MHDD (Bootable Tool)

Runs outside the OS (from USB/CD)

Advanced tool for diagnosing low-level problems

Ideal for IT professionals and data recovery experts

4. Clone the Drive and Replace

If the damage is growing or the drive is critical:

Clone with tools like Macrium Reflect, Clonezilla, or ddrescue

Replace the failing drive

Transfer data to a new drive

C. Reformatting and Low-Level Formatting

Warning: Formatting erases all data, so back up first.

1. Full Format (Not Quick Format)

A full format checks for bad sectors and marks them.

Steps:

Open This PC → right-click the drive

Click Format

Uncheck “Quick Format”

Choose file system (NTFS or exFAT)

2. Manufacturer Tools (Low-Level Format)

Some drive manufacturers offer utilities to perform a zero-fill or low-level format:

Western Digital – Data Lifeguard Diagnostics

Seagate – SeaTools

Samsung – Magician Software

Toshiba – Storage Utilities (limited)

These tools:

Overwrite all sectors with zeroes

Mark irrecoverable sectors

Help revive inaccessible drives

D. Cloning a Drive with Bad Blocks

If your goal is to recover data, clone first and repair later.

Recommended Tools:

ddrescue (Linux/Unix)

HDClone (Windows)

AOMEI Backupper

These tools skip unreadable sectors and copy everything else, minimizing further damage.

When You Should Replace the Drive

No matter how effective your tools are, a hard drive with increasing bad sectors is a ticking time bomb. You should consider replacing the drive if:

SMART data shows reallocated sectors growing

Frequent freezing or crashing continues after repair

Important files are becoming corrupted

Repair tools fail to complete scans

Preventing Bad Blocks in the Future

While bad blocks can’t be entirely avoided, the following steps reduce the chances:

Always shut down properly

Use a surge protector

Avoid physical movement while the drive is active

Regularly check drive health with SMART tools

Keep the drive cool and dust-free

Don’t let drives run at 100% capacity

Backup critical data regularly

Using SSDs vs HDDs

It’s worth noting:

SSDs can develop bad blocks too, but they handle them differently

SSDs have wear-leveling mechanisms to prolong life

HDDs show more signs of degradation over time

For high-performance and long-term use, consider upgrading to an SSD.