Then I found ‘Sync’ – a Java command-line application for synchronization.
While there is no UI for the application, which can be painful for some people, the app is a boon for me. I have created scripts – batch files – to sync data. With this batch files, I connect the portable drive, navigate to the backup folder on the portable drive and fire the scripts one by one. In this method, the scripts do not need to refer to the destination drive letter. They are referred by ‘.’. All that is needed is the source directory, which resides on internal HDD and does not change.
While I do not recollect where I got the source from, I would like to thank the author for this app.