Bad Sectors: When to Back Up and When to Call for Help
Bad Sectors on Drive: When to Back Up and When to Call for 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 repaired? 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 repaired? 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 | Unrepairable sectors |
When it's critical:
- Reallocated Sector Count > 0 and growing
- Current Pending Sector > 0
- Uncorrectable Sector Count > 0
Symptoms During Use
- Slowdown: Drive tries to repeatedly read 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 CHKDSK
- Drive makes unusual sounds – CHKDSK will worsen situation
- 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 backup – DON'T RUN CHKDSK. Contact us for free diagnostics.
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 recognized 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 Call an Expert
Decision Tree
Does drive make unusual sounds?
├── YES → Shut down immediately, call expert
└── NO → Continue below
SMART values critical (Current Pending > 0, rapid growth)?
├── YES → Call expert
└── NO → Continue below
Do you have backup of important data?
├── YES → You can try CHKDSK or backup
└── NO → Call 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 specialized 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 minimizes further damage
- Working with copy – original doesn't deteriorate
- Experience – we know when to stop and when to continue
Success Rate
- Minor damage (< 100 sectors): 95%+
- Medium damage (100-1000 sectors): 85-95%
- Severe damage (1000+ sectors): 70-85%
- Critical damage + mechanical problems: 50-70%
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 preventively replacing a drive older than 4-5 years, even if it still works. Cost of a new drive is a fraction of data recovery cost.
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 repaired. They may disappear from statistics (remapping), but 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 backup, don't experiment. We'll gladly perform free diagnostics and tell you the options.
Email: info@datahelp.eu Pickup + Diagnostics: €45 | Pay only for results