FreeFileSync Forum

@therube If you like to investigate more, it did that only to sync.ffs_db not to other files, but files created by some other specific programs where also corrupted. What they had in common was that they where all written to the drive in a highly parallel order, not sequentially like byte, by byte ...

I think it's a file system bug as you said, since I used WinBtrfs driver on Windows, which is buggy and causes CRC errors on parallel write operations. That's a shame, since Btrfs is very nice file system for backup storage :(

When the target hard drive has cluster size bigger than the sync.ffs_db file itself, the FFS fills the remaining empty space with 0x00, which then produces CRC error.

Cannot read database file "path\to\sync.ffs_db".
File content is corrupted. (invalid checksum)

I'm using Btrfs formatted drive ...