Finding out a disk is bad after it crashes can often prove disastrous. To be warned of a failing disk is something we all would appreciate. This can be done via [http://smartmontools.sourceforge.net/ smartmontools]], a free software package that can monitor S.M.A.R.T. attributes and run hard drive self-tests. Basically, S.M.A.R.T. may give you enough of a warning that you can safely backup all your data before your hard drive dies. Obviously, nothing replaces regular backups, but it's absolutely better than knowing nothing!