I dropped my external HDD (WD My book 2TB, non-portable) from 1m (3ft) height on the hard floor. Now there seems to be no problem, but is there any way that I can check if it is okay?
In the old days, I remember that there were utilities that check 'bad sectors'. Does this apply to modern external HDD?
There are a number of disk scanning utilities, but you haven't told us which OS you're running. As a Kubuntu user, I'd usually use the "scan for errors" in a partition utility like gparted or KDE Partition Manager. In Windows, there is a "surface test" option available for Scandisk that will check for bad sectors.
With a dropped HDD, however, you need to do this regularly for a while, to watch for changes in the bad sector count (or, ideally, bad sectors appearing in a pattern that corresponds to physical damage like a head skidding across the platter -- which I've seen, several years ago; a location map of the bad sectors made a nice arc).
As noted in a comment, the SMART system includes internal records of number of read retries (an indicator of data surface wear or progressive damage) and bad sector count (another indicator of damage) and will be much faster than running multiple Scandisk surface tests. Check on it daily for a week or so, and weekly for the next year -- by that time, you'll be able to tell if you need to consider replacing the hard disk (you needn't replace the entire external unit, just the actual drive inside, if that's the case).
