Might take a little while; but, yes, a bit worrying...

Try OS X's Disk Utility instead otherwise you'll need something like Disk Warrior or Tech Tool Pro. If anything shows disk damage then the disk is on the way out (in my experience external drives last no longer than a couple of years). You might get a few months or a few days out of it; but be prepared to buy a new external drive...

Posted By: BerlinCanary, Jan 22, 21:58:33