File synchronization is the process of ensuring that two or more locations contain the same latest files. If you add, change, or delete files from one location, the synchronization process will add, change, or delete the corresponding files in another location. Synchronization can be "two-way" or "one-way". What is One-Way Synchronization and Two-Way Synchronization？ Two-Way Synchronization This synchronization process copies files in both directions to coordinate changes as needed. It is expected that the file will change in both locations. These two positions are considered equivalent. Example: If the file is newer in location A, it will be copied to location B. However, if the file is newer in location B, it will be copied to location A. Similarly, if a file is deleted from location A, the file will be copied. Also deleted from position B, and vice versa. One-Way Synchronization The file can only be changed in one location. To coordinate changes, the synchronization process copies files in only one direction. These two positions are not considered equivalent. Ø NE location is considered the source and the other is considered the target. The file is pushed away from the source to target . It is said that Source has been mirrored to Target. This will create an exact 1:1 copy of all files in the "source to target". Since only new files are changed, this is very useful and effective for backup. Example: If the file is newer in location A , it will be copied to location B . However, if the file in location B is newer, it will not be copied to location A. Similarly, if a file is deleted from location A, it will be deleted from location B. Auto-Sync File synchronization can be run automatically at irregular intervals, ie every 10 minutes, every 2 hours, etc., at scheduled times , in real-time . Detected at startup or shutdown. Common File Synchronization Solutions Synchronization between computers connected to a local network . The computer can be a laptop, desktop, workstation, server. For cross-computer sharing of selected folders, use Windows file sharing and sync use and vice versa. Synchronization between computers connected to the Internet . This requires a VPN tunnel. The computer can be a laptop, desktop, workstation, server. Synchronization between computer and external drives . Synchronization between computer and NAS. The ultimate goal is to ensure that the selected folder on the computer and/or drive has the same latest files. Synchronization between unconnected computers For computers that are not connected to the network, you can use a portable USB drive to synchronize. If the files on the home computer must be synchronized with the files on the computer at work, you can synchronize the PC-1 with a portable USB drive, and then connect the PC-1 with the portable The USB drive is synchronized to achieve synchronization. The drive works normally and performs the same synchronization between the PC-2 and the portable USB drive. At the end of the process, the same latest file will be on both PCs and USB drives, which is useful for data backup.

Synchronous Transfer Synchronous transmission is the data transfer in units of data frames. Frame synchronization signals in the form of characters or bit combinations can be used. The transmitter or receiver provides a clock signal dedicated to synchronization. In short-distance high-speed large file transfer, the clock signal can be transmitted by a dedicated clock line. When the computer network adopts the synchronous transmission method, the clock synchronization signal is often embedded in the data signal frame to achieve clock synchronization between the receiver and the transmitter. In digital communication, synchronization is very important. When the transmitter transmits data information to the receiver through the transmission medium, for example, each time a character data signal is sent, the receiver must recognize the start bit and end bit of the character data signal. To correctly read each bit of the data signal of the character at the appropriate time, this is the basic synchronization problem between the receiver and the transmitter. When sengding data signals in data frames, to ensure the integrity and accuracy of the transmitted signal, in addition to requiring the receiver to be able to recognize the start and end of the signal corresponding to each character , to ensure that the reading starts and ends at the correct time Retrieving the signal means maintaining the integrity of the transmitted signal. It is also required to keep the clock and the transmitter at the same frequency to ensure that the number of signal units reads per unit time is the same, that is, to ensure the accuracy of the transmitted signal. Therefore, when transferring data signals in data frames, the transmitter is required to take the following two measures for the transmitted signals: ①Add a start signal and a stop signal different from the data signal before and after the corresponding signal of each frame of data; ② Add a clock synchronization signal before the data signal of each frame to control the clock synchronization of the receiver. Asynchronous Transmission Asynchronous transmission is the transmission of data in units of characters, using character synchronization signals in the form of bits. The transmitter and receiver have independent clocks , and neither side provides clock synchronization signals to the other side. The sender and receiver of the asynchronous transmission do not need to coordinate before the data can be transmitted: the sender can move data at any time, and the receiver must be ready to receive data at any time. The asynchronous transmission mode is generally adopted between the computer host and the input and output devices. Such as a keyboard, a typical RS-232 serial port : the sender can send a character at any time . The Advantages and Disadvantages of Asynchronous and Synchronous Data Transmission 1. Asynchronous transmission is the character-oriented transmission, while the synchronous transmission is bit-oriented. 2. The unit of asynchronous transmission is character and the unit of synchronous transmission is a frame. 3. Asynchronous transmission seizes the opportunity of re-synchronization through the start and stops codes of character start and end, while synchronous transmission extracts synchronization information from the data. 4. The asynchronous transmission has lower requirements on timing, and synchronous transmission often coordinates timing through a specific clock line. 5. Asynchronous transmission is less efficient than synchronous transmission. To Sum Up Both asynchronous transmission and synchronous transmission have the above basic synchronization problem: character synchronization or frame synchronization signals are generally used to identify the start and end of transmitting character signals or data frame signals. The main difference between the two is whether one of the transmitter or receiver sends a clock synchronization signal to the other party.