disableFsync is an advanced folder setting that affects file modifications. Normally, when a file has been modified Syncthing calls fsync() on that file and the containing directory. This forces file data that is cached in RAM to be flushed to disk. This ensures that data is safely stored on disk and thus prevents data loss in the case of a power failure soon after file modification.

There is however a performance cost to doing this, especially on rotating disks or network filesystems, especially syncing many small files. Disabling fsync() improves performance at the price of risking data loss in a power failure situation.


This option should normally be set to false.