This morning I copied around 200GB of data to a quite old USB2.0 1TB external drive. The copying took around 2 or 3 hours. Afterwards I unmounted & the unmounting is still going on (after more than 12 hours).
I am afraid to interrupt the unmounting process & retry it. Is this a common problem? How should I proceed in order to not corrupt some of the data that I copied onto the external drive. I am running lubuntu 14.04