Runtime filesystem consistency checking

Adding to what James said above me, I think you might want to look into installing the SMART tools to query your drive. The "smartctl" tool will read out and display the various statistics the drive's been collecting about corrected errors and remapped sectors.

It will also let you fire up background health checks (these can take quite a long time to complete -- as long as a day, as I recall) that may help turn up other problems.