This means that there is an hardware failure on the disk, it will fail in the next hours or days or has already failed. There is not much you can to do.
If you can still access the disk data, stop all services and backup the disk data *immediately*. Don't power off the box, as the disk might fail completely at the next power-up.
Further questions should be made at the 'smartmon-tools' forums, enclose the log from Disk->Utilities->Health->Show Status.