Bad Sectors: When to Back Up and When to Get Help
Bad Sectors on a Hard Drive: When to Back Up and When to Get Help
Windows reports disk errors. CHKDSK found bad sectors. CrystalDiskInfo is glowing red. What now?
Bad sectors are one of the most common hard drive problems. The good news is that their presence doesn't necessarily mean immediate data loss. The bad news is that the number of bad sectors never decreases – it only grows.
What Are Bad Sectors
A sector is the smallest unit for storing data on a hard drive – typically 512 bytes or 4,096 bytes. Every drive has billions of them.
A bad sector is an area that cannot be reliably read or written. The magnetic layer may be damaged, or it may be a logical error.
Why Bad Sectors Occur
- Manufacturing defects: Every drive has a certain number of bad sectors from the factory (marked and hidden)
- Wear: The magnetic layer degrades over time
- Impacts: Even a small impact can damage a local area
- Overheating: Thermal stress damages the platter surface
- Sudden disconnection: Interrupted write can damage a sector
Soft vs Hard Bad Sectors
There are two types of bad sectors and it's important to distinguish them.
Soft (Logical) Bad Sectors
What it is: The sector itself is physically fine, but the data in it is corrupted or inconsistent. Typically the checksum (ECC) is missing or wrong.
Causes:
- Sudden computer shutdown during write
- Software error
- Malware
- Operating system error
Can it be fixed? Often, yes. The operating system or tools like CHKDSK can rewrite the sector and restore functionality.
Hard (Physical) Bad Sectors
What it is: Physical damage to the magnetic layer of the platter. The sector simply cannot be used.
Causes:
- Head crash (head contact with platter)
- Material degradation
- Manufacturing defect
- Overheating damage
Can it be fixed? No. The drive has a reserve area where it remaps bad sectors (reallocated sectors). But the number of replacement sectors is limited.
How to Detect Bad Sectors
SMART Values
The SMART system monitors drive health. Key values for bad sectors:
| SMART ID | Name | What It Means |
|---|---|---|
| 05 | Reallocated Sector Count | Number of remapped bad sectors |
| 196 | Reallocation Event Count | How many times remapping occurred |
| 197 | Current Pending Sector | Sectors waiting for remapping |
| 198 | Uncorrectable Sector Count | Sectors that could not be read or corrected |
When it's critical:
- Reallocated Sector Count > 0 and growing
- Current Pending Sector > 0
- Uncorrectable Sector Count > 0
Symptoms During Use
- Slowdown: the drive repeatedly tries to read a problematic sector
- Freezing: System waits for drive response
- Errors when copying: "Cannot read source file"
- Corrupted files: Files won't open or have wrong content
- Blue screen: KERNEL_DATA_INPAGE_ERROR, NTFS_FILE_SYSTEM
CHKDSK – Yes or No?
This is a critical question. CHKDSK can help, but it can also harm.
When CHKDSK Can Help
- Drive is otherwise healthy (SMART OK)
- You only have soft bad sectors
- You have a data backup
- Problem occurred after sudden shutdown
When NOT to Run CHKDSK
- Drive makes unusual sounds – CHKDSK will make things worse
- SMART reports mechanical problems – risky operation
- You don't have backup – CHKDSK can cause further data loss
- Rapidly growing bad sector count – drive is dying
What CHKDSK Does
chkdsk /r
- Scans all sectors on drive
- Identifies bad sectors
- Moves readable data from bad sectors
- Marks bad sectors as unusable
Problem: With mechanical damage, this intensive reading can:
- Cause further head damage
- Extend scratches on platter
- Heat the drive
- Worsen overall state
Our Recommendation
If you suspect mechanical damage or don't have a backup – DON'T RUN CHKDSK. Request a free case assessment instead.
When There's Still Time to Back Up
If the drive still works and the bad sector count isn't critical, you have a chance to copy data yourself.
Signs It's Time to Act
- SMART warns, but drive works
- Reallocated Sector Count < 100 and not growing fast
- No unusual sounds
- Drive is recognised and readable
Safe Backup Procedure
- Prepare target drive – new, healthy HDD or SSD
- Use robust tools:
robocopy(Windows) – handles errors better than Explorerddrescue(Linux) – best for problematic drives
- Start with most important data
- Don't run demanding operations – defragmentation, antivirus scan
- Monitor drive – if it starts clicking, stop immediately
Robocopy Command for Safe Backup
robocopy C:\ImportantData D:\Backup /E /R:1 /W:1 /LOG:backup.log
/E– including subfolders/R:1– only 1 retry on error (not 1 million)/W:1– wait 1 second between attempts/LOG:– save log for verification
When to Contact an Expert
Decision Tree
Does drive make unusual sounds?
├── YES → Shut down immediately, contact an expert
└── NO → Continue below
SMART values critical (Current Pending > 0, rapid growth)?
├── YES → Contact an expert
└── NO → Continue below
Do you have backup of important data?
├── YES → You can try CHKDSK or backup
└── NO → Contact an expert (risk of data loss)
When It's Urgent
- Bad sector count growing rapidly (tens daily)
- Drive getting slower
- Sounds appearing
- System crashes when accessing certain files
Professional Data Recovery from Drive with Bad Sectors
How We Work
- Diagnostics – we determine extent and distribution of bad sectors
- Sector copy – we use specialised hardware (PC-3000, DeepSpar)
- Intelligent reading:
- Skipping problematic areas
- Returning to them with different strategies
- Adjusting reading speed
- Monitoring drive temperature
- Data reconstruction – we restore file system and files
Advantages of Professional Approach
- Hardware allows finer control than regular computer
- Skipping bad areas minimises further damage
- Working with copy – original doesn't deteriorate
- Experience – we know when to stop and when to continue
What Affects the Outcome
There is no universal success rate – every drive is different. As a rule, the fewer bad sectors there are and the sooner the drive reaches us, the more data we can read. Extensive surface damage, especially combined with mechanical problems, reduces what can be recovered. That is why it pays to stop using the drive as soon as the bad sector count starts to grow.
Prevention
Regular Monitoring
Install a SMART monitoring tool:
- Windows: CrystalDiskInfo (free)
- macOS: DriveDx (paid)
- Linux: smartmontools
Set alerts for critical value changes.
Regular Backups
Bad sectors will come sooner or later. Backup is the only real protection.
- 3 copies of data
- 2 different media
- 1 offsite
Planned Replacement
Consider replacing a drive older than 4–5 years as a precaution, even if it still works. A new drive costs a fraction of a data recovery.
FAQ
How many bad sectors is too many?
There's no magic number. More important than absolute count is the trend:
- 50 stable sectors for years = OK
- 5 sectors that increased to 50 in a month = problem
Can bad sector count decrease?
No. Physically bad sectors cannot be fixed. They may disappear from the statistics (remapping), but the reserve area has limited capacity.
How long will a drive with bad sectors last?
Cannot be predicted. May work for years, or fail tomorrow. Depends on cause and degradation speed. Once you have bad sectors, plan replacement.
Is it better to replace HDD with SSD?
SSDs don't have mechanical bad sectors, but have their own problems (cell wear, TRIM). For important data, the best is combination: SSD for regular use + backup on HDD or cloud.
Need to Recover Data?
If your drive shows bad sectors and you don't have a backup, don't experiment. Register your case online – the initial assessment is free and you receive a binding quote before any recovery work starts. No Data, No Fee. Send the drive to our lab with a tracked, insured carrier, hand it in personally in Prague, Vienna or Bratislava, or book our optional insured DPD pickup (€45).
Email: info@datahelp.eu