Any backup software will compare the file size and the last modified date to determine if a file should be backed up. This technique works fine with small files. However, copying the entire file is not practical for large files on a daily basis.
Copying part of the file that has been modified
Often users have to backup large files on a daily basis. Copying the entire file can be extremely time consuming and can potentially consume huge network resources.
Rather than copying the entire files over and over again, Syncrify determines that part of the file that has been changed and just copies the delta. In the background, it implements the Rsync algorithm that has been in use in the Unix/Linux community for years and offers an excellent mechanism to copy just the part of the file that has been modified.
Syncrify uses the Rsync algorithms over HTTP(S) - meaning if you have a backup a 10 GB file every night, Syncrify will intelligently determine the parts of the file that has been changed and copy just that. Hence the actual number of bytes transferred will be a small fraction of the entire file.
How does Syncrify determine what part to copy?
Syncrify works on a client/server model. Both client and server communicate with each other and divide a file in multiple chunks, called a Delta. These Deltas are then compared on each end. Finally, Deltas that don't match are sent to the server.