
Modern SCSI disks have it too if they’re SCSI 3 or newer. It happens that inside the disk chipset there are routines to check parameters of disk health: spin-up time, number of read failures, temperature, life elapsed… And all of those parameters are not only registered by the disk chipset, but they have designated security limits and both parameters and limits can be checked by software who access the disk using the appropriate I/O instructions.
And that software is smartctl, a piece of the smartmontools deb package.
[Fuente noticia completa.: http://debaday.debian.net/2008/10/12/smartmontools-control-the-health-of-your-hard-disk/]