FreeFileSync can be set up to issue multiple file accesses
in parallel. This speeds up synchronization times dramatically in
cases where single I/O operations have significant latency
(e.g. long response times on a slow network connection)
or they cannot use the full bandwidth available
(e.g. an FTP server enforcing a speed limit for each connection).
The number of parallel file operations that FreeFileSync should use
can be set up for each device individually
in the Comparison Settings
It is evaluated for all folder pairs of a configuration as follows:
- During comparison FreeFileSync groups all folders by their root devices.
For example, consider a configuration with two folder pairs and parallel file operations set up:
FreeFileSync will put the folders C:\Source and
into the same group and allow only 1 file operation at a time.
Folder D:\Target will be traversed using 2 operations,
and E:\Target using 3 operations at a time.
In total FreeFileSync will be scanning all four folders
employing 6 file operations in parallel.
- When synchronizing a folder pair FreeFileSync
will use the maximum of the number of parallel operations
that the two folders support.
In the previous example the folder pair
C:\Source ↔ D:\Target
will be synchronized using 2 parallel operations, and
C:\Source2 ↔ E:\target
will be using 3.
FreeFileSync implements parallel file operations by opening multiple connections to a device.
Some devices like SFTP servers have limits on how many connections they allow and will
fail if too many are attempted; see (S)FTP Setup