FreeStyleThink & mirror

[JPR_Project]

Hello everyone,
I'm experiencing a serious issue with FreeFileSync when comparing files in Mirror mode.
Problem description:
I had all my English courses from several years stored on my external hard drive. I bought a new external hard drive (4 TB). I wanted to transfer files using mirror mode from L → F. I have tons of files, including MP3/WMA/M4A and other formats (PDF...), that have completely disappeared from my L drive. How and WHERE can I recover them?
What I observe:
• Error message: « Unable to read database file "F:\sync.ffs_db". File content is corrupted (invalid header.) »
• The BatchRun.ffs_Batch file from 27/07/2026 also shows « invalid header »
System setup:
• Operating System: Windows 11, version 24H2
• FreeFileSync version: 14.10 64 Bit (28/06/2026)
• Synchronization type: **Mirror one-way L:\ → F:**
• Storage involved: **External hard drives L:\ and F:**
• Comparison method used: Not specified (batch file corrupted)
What I've already tried:
• With ChatGPT's help, I tried several solutions. I was provided with a list of OK files and empty files in an Excel file: AUDIT_AUDIO_ANGLAIS_20260801_102723.xls
• I ran a recovery test using RECUVA/DMDE/, but I’m still lefet with a lot of EMPTY files.
• [Add here any other attempts: restart, disk check, etc.]
Goal:
I need to RECOVER as soon as possible my years of English courses, especially all audio files. My goal is to restore files from my source folder to my destination, with reliable comparison.
Attachments:
• Screenshot of the error [to add on the forum]
• Excel audit file (if allowed)
Thank you in advance for your help! This is very urgent for me.
Best regards,
JPR_Project
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[xCSxXenon]

This sounds like your old drive was already failing and the data was corrupted by the time you copied it

[JPR_Project]

Thanks for your answer. I'm French. No, it's working fine as usual so far.

[JPR_Project]

It's strange that the missing audio files are empty.

[Zenju]

Some food for thought: One prime candidate for data corruption is forgetting to unmount an external drive, if the file system is buffered, e.g. the default for NTFS. "No unmount" means the data in the OS cache is lost, leaving behind empty files or files filled with zeros.

[therube]

> The BatchRun.ffs_Batch file from 27/07/2026 also shows « invalid header »

post the contents of your .ffs_Batch (it is only a "text" file, or should be ;-))

> Screenshot of the error [to add on the forum]

it never made it up here

> the missing audio files are empty

"missing", but they ARE there, but 0-bytes, is that it?

if you take 1 of these "missing audio files" (say Bell 20230825), are you able to open & play it successfully on both the L: & F: ends?

[JPR_Project]

I'm French and it's very difficult.

[JPR_Project]

20230825===>EMPTY

[JPR_Project]

Folder Françoise DEHANT ===>EMPTY

All files==>MP3, WAV & M4a ===>EMPTY

[JPR_Project]

Almost all of my MP3 files are EMPTY.

[JPR_Project]

No response ?

[JPR_Project]

How and WHERE can I recover my files....No one has given me a SINGLE solution since then!
How and WHERE can I recover my files....No one has given me a SINGLE solution since then!