Recovering lost files from an external hard drive is often possible with the right tools and techniques. External hard drives can fail or become corrupted, leading to data loss, but much of the lost data can be recovered by using data recovery software or services.
What causes file loss on external hard drives?
There are several common causes of file loss or corruption on external hard drives:
- Accidental deletion – Files may be inadvertently deleted by the user.
- Format or partition errors – Errors during formatting or repartitioning can cause data loss.
- File system corruption – The file system managing the files on the drive becomes corrupted.
- Bad sectors – Parts of the drive become physically damaged and unusable.
- Malware or virus infection – Malicious programs can attack files on the drive.
- Improper ejection – Removing the external drive without properly ejecting can lead to errors.
- Physical damage – Dropping or impacting the drive can damage components.
- Water damage – Liquids can short circuit and ruin the drive’s electronics.
Factors affecting file recovery chances
The chances of recovering lost files depend on several factors:
- Cause of data loss – Some causes, like accidental deletion, make recovery more likely.
- Drive failure type – A physically damaged drive is harder to recover from than a software error.
- Drive usage after data loss – Continued use lowers chances; the drive should be immediately removed and recovered.
- Drive make and model – Some hard drives are designed to assist in data recovery.
- File system – Formats like NTFS often keep backup copies of files and metadata.
Best file recovery methods
Here are some steps to take to recover lost data from an external hard drive:
- Stop using the drive immediately if data loss is suspected, to avoid overwriting files.
- Connect the drive to another system if it has failed completely on its original system.
- Scan the drive with data recovery software that can read the file system, like Disk Drill or Stellar Data Recovery.
- Select file recovery options: decide if lost files should be restored to another drive or stored as a disk image.
- Preview found files before recovery to avoid recovering corruption or unnecessary files.
- Restore the files to a healthy drive. Organize them properly once recovery is complete.
Software File Recovery
Data recovery software scans the external drive and combs through its data, looking for intact copies of lost files it can restore. It uses techniques like:
- Searching for lost file records in the file system metadata.
- Looking for data patterns associated with common file types like JPEGs and documents.
- Accessing protected backup copies of files the file system may keep.
- Bypassing damaged file system structures to directly read disk contents.
The right software can restore files when they have been accidentally deleted, after a format, or due to file system damage. However, it cannot easily recover from physical media damage like bad sectors.
Professional Data Recovery Service
For difficult cases like drives with mechanical damage, a professional data recovery service may be required. These experts use techniques like:
- Opening the drive in a cleanroom environment to avoid dust contamination.
- Repairing or bypassing failed drive components like the controller or motor.
- Imaging the drive and extracting data manually from the full disk image.
- Using specialized tools and advanced skills to manually access the underlying storage media.
Professional services can recover data in cases where DIY software fails, but they typically charge several hundred dollars at a minimum.
Sending Drive to Manufacturer
For some external hard drives that fail under warranty, users may be able to send the drive back to the manufacturer for recovery. The manufacturer has intimate knowledge of the drive hardware, and may be able to repair it and extract data.
However, there are some downsides to manufacturer recovery:
- Only an option if the drive has an intact warranty.
- Recovery can take weeks due to shipping times.
- No guarantee data can be recovered, if issues are very serious.
- Replacement/refurbished drive may be provided instead of original.
Best practices to avoid data loss
Following good practices when using external hard drives can help avoid data loss scenarios:
- Always eject the drive properly before disconnecting.
- Keep backups of important data on a separate drive or the cloud.
- Be careful not to expose drive to physical shocks or drops.
- Check drive health periodically with disk utilities like CHKDSK.
- Keep antivirus software active to prevent malicious infection.
- Avoid sudden power interruptions when the drive is connected.
Can lost files be recovered after reformatting the drive?
Reformatting an external hard drive erases all data on it by reinitializing the file system and partitioning. However, data recovery software can still potentially restore lost files after reformatting in some cases.
When a drive is reformatted, the following happens:
- The old file system structures are erased, like the partition table.
- A new blank file system is created, like FAT32 or NTFS.
- The logical mapping of disk data is reset.
However, the underlying data itself is often still intact until it gets overwritten by new files written to the reformatted drive.
Therefore, recovery software can:
- Scan the drive’s sectors for identifiable file patterns.
- Extract files even without file system data like filenames.
- Use the structure of known file types to reconstruct files.
The chances of recovery depend on how much data was written after reformatting. But in many cases, a sizable portion of files can still be successfully recovered.
Improving chances after reformatting
To improve chances of recovering data after a reformat, users should:
- Avoid writing new data to the drive.
- Use recovery software as soon as possible.
- Look for signs of intact files like image thumbnails.
- Focus recovery on large files which have predictable structure.
Can files be recovered after full drive encryption?
Recovering files from a fully encrypted external hard drive without knowing the password or encryption key is very difficult and near impossible with current technology.
Full disk encryption, like BitLocker on Windows or FileVault on Mac, encrypts every single file on the drive. Without the encryption key, data appears completely random and unrecoverable.
Encrypted drive recovery requires:
- Knowing the user password or recovery key used to decrypt the drive. Otherwise, decryption is mathematically infeasible.
- Access to decryption tools built into the operating system, like BitLocker on Windows.
- Finding encryption keys stored in system backups, if available.
If the drive is partially encrypted, or if only certain files are encrypted, then recovery of non-encrypted data may still be possible.
Some paid recovery services claim to crack encryption keys, but success is unlikely. For a fully encrypted drive, creating a usable backup is the best practice.
Recovering after factory resetting external drive
Many external hard drives come with factory reset functions to erase user data and restore the drive to a like-new state. Recovering files after such a reset can be challenging but is sometimes possible.
Factory reset typically involves:
- Overwriting part or all of the drive with zeros to erase user files.
- Reinstalling the drive’s firmware, partition structures and file systems.
- Restoring default software bundles that came with the drive.
The extent of data erasure depends on reset thoroughness. Light resets may retain recoverable user files while thorough resets overwrite all data areas.
Recovery success depends on:
- Reset type – light or standard resets are better than thorough options.
- How many passes of overwriting were done – more passes make recovery harder.
- Whether device areas were reset where files may survive a full reformat.
With a light factory reset, a quick scan after rebooting can find recoverable files. But a full overwrite reset likely requires professional destructive recovery methods.
Recovering files after full deletion
Files deleted completely from an external drive can still be recovered in some circumstances using specially designed undelete software.
When files are first deleted on a drive, several things happen:
- Filesystem metadata like filenames and locations are erased.
- Disk space used by the files is marked as available for reuse.
- Actual file contents remain intact until storage is overwritten.
Therefore, recovery software can:
- Scan disk sectors for familiar file patterns from things like photos, documents, and compressed files.
- Attempt to reconstruct filesystem metadata like original folder structures.
- Extract files from unallocated disk space not yet overwritten.
However, without original filenames and folders, recovered files may need manual sorting and renaming.
Success rates improve if:
- No new files were written after deletion, preventing overwrite.
- File contents are recognizable by patterns.
- The original filesystem is intact enough to preserve metadata.
With fast action after deletion, before any new writes occur, deleted files can often be fully restored with their original filenames and folder paths.
Physical recovery from drive platters
As a last resort when all else fails, platter-level recovery may be an option for mechanical external hard disk drives. This invasive physical recovery method can extract data directly from the disk plates and head assembly – but it’s technical, risky and expensive.
How physical data recovery works:
- The drive is opened in a professional clean-room environment to avoid dust contamination.
- The platters are removed from the damaged drive chassis without being scratched.
- They are inserted into a specialized recovery rig to read data directly off the magnetic surfaces.
- Weak magnetic data signals are processed and converted to binary data.
- Data is reconstructed into usable files using extensive skills and software.
This approach can recover data when all electronics have failed. But it has downsides:
- Extremely technically challenging – requires advanced skills in physics and engineering.
- Low success rates and no guarantee of finding files intact.
- Very expensive, with costs potentially exceeding $1000.
Nonetheless, platter-level recovery represents a last chance when all else has failed on a damaged yet important external hard disk drive.
Conclusion
Recovering lost files from external hard drives is often possible with the right approach and tools. While software recovery works well in many cases, difficult mechanical failures may require professional data recovery services for any chance of success.
Prevention is always the best way – following good external drive practices helps avoid data loss. But when disaster strikes, understanding the different recovery options available can significantly improve the chances of restoring those critical files.
