By Ailsa / Last Updated August 25, 2020

One-way vs Two-way Data Synchronization

One-way sync will sync newly added or changed files from source directory to the destination directory, which means the files changed in the destination will not be synced back to the source. Therefore, it will protect you all the files in the source against the deletion or edition by human error.

One Way Sync Vs Two Way Sync

As you can imagine, two-way sync (bidirectional sync) will sync files both ways, which means all the newly added or changed files in source will be synced to the destination, meanwhile, the added or updated files in the destination will be synchronized to the source. Two way sync will always keep the files in source and destination exactly the same.

Why Need Two Way Synchronization?

You need the two way synchronization to sync files both ways in some circumstances, such as:

  • Two-way sync between two different databases to use the data more convenient.

  • Sync two NAS (Synology or QNAP) from each other to share the files on two sides.

Or other situations you may need the two way data synchronization. How to perform two way file sync easily in Windows 10/8/7?

Best Two-way Sync Software for Windows 10/8/7

If you would like to do Bi-directional sync (two way sync), it’s highly recommended to use the best two way sync software - AOMEI Backupper Professional, which is designed for Windows XP, Vista, 7, 8, 8.1 and 10, including 32-bit and 64-bit, to sync files easily.

AOMEI Backupper Professional as the comprehensive file synchronization software, allows you to do the following:

  • Sync files to multiple destinations: It allows you sync files to local disk, external hard disk (HDD or SSD), USB flash drive, thumb drive, CD/DVD, network share folder or NAS, even the clouds, like Google Drive, OneDrive, Dropbox, Box, etc.

  • Different sync features to choose: It offers you the different sync features to meet your demands accordingly, like basic sync, mirror sync, real time sync, and two way sync.

  • Set it and forget it: You could set up a two way sync task with Schedule option to automatically run via daily, weekly, monthly, USB plug in and event triggers.

  • Real time sync: It’s capable of syncing files from the source location to the destination in real-time, with no delays.

Please download the best two way sync software 30 day free trial to have a try:

How to Perform Two-way Sync Easily in Windows 10/8/7?

To show you how to set up a two way data synchronization task with the best file synchronization software - AOMEI Backupper Professional, please refer to the two way data synchronization best practices (take NAS to NAS sync for example):

Step 1. Launch the two way sync software - AOMEI Backupper Professional, select Sync > Two Way Sync in turn.

Two Way Sync

Step 2. Click + Add Folder > Share/NAS > Add Network Location > input the Display Name and the Network Path (IP address of the source NAS) and hit OK to add the source NAS, and then choose the folders you would like to sync.

Add Folder Share NAS


Step 3. Select another NAS as destination: click the inverted triangle icon > Select a network location > Add Network Location > input the Display Name and the Network Path (IP address of the Destination NAS) and choose a folder in destination NAS to save the folders from the source location.

Select A Netwrok Location


Step 4. Tap Start Sync >> to run the two way data synchronization task.

Start Sync NAS To NAS

There are some optional settings you could customize:
✍Options: This setting allows you to comment the sync task, run specified program or script before or after the sync task, enable email or SMS notification, etc.
✍Schedule setting offers you the option to automatically run the sync task via once, daily, weekly, monthly, USB plug in, event triggers. USB plug in will automatically detect the USB flash drive related with the sync task once the USB is plugged in to the computer, it will sync the changed files since the last sync immediately. Event triggers allows you to trigger the sync task via the four events, User logon, User logoff, System startup, System shutdown.

It’s easy for you to perform the two way data synchronization task, right?

How the Two Way Sync Works?

To make it clear how the two way sync works in Windows computers, you may want to know the two way sync algorithm, let’s find out:

The source directory and the target directory will compare with the previous synchronization result during synchronization, and get the changed files, and then compared with the files changed in the other directory. Then, sync files with the below algorithm:

1. When both directories change:

  • If both directories modify a file, compare the update time of both directories, and the new file overwrites the old file.

  • If one directory modifies a file and the other deletes the file, the modified file will be synchronized to the other directory.

2. When only one directory changes:

  • If one directory deletes a file, the other deletes the file too.

  • If one directory modifies a file, the other also need to modify the file.

  • If one directory adds a certain file, the other adds this file too.

The Epilogue

As we showed above, the two way data synchronization is easy for all of us, especially with the help of AOMEI Backupper Professional. And the two way sync could help you to get the latest version of files anytime.

Besides, AOMEI Backupper allows you transfer files from one computer to another computer, migrate Windows 10 OS to SSD without reinstalling, command line backup/restore/clone for advanced users, dynamic disk volume backup/restore/clone, etc.