SMART originated from IBM's Predictive Failure Analysis technology. They broke failure into predictable and unpredictable (obviously it's hard to develop hardware for unpredictable failures such as a logic component frying). However, IBM (and other manufacturers) decided that there were enough gradually degrading problems with detectable warning sign to warrant creating some early warning tech.
The most common error reporting methods are among the following:
- Head Flying Height: A downward trend in flying height will often presage a head crash.
- Number of Remapped Sectors: If the drive is remapping many sectors due to internally-detected errors, this can mean the drive is starting to go.
- ECC Use and Error Counts: The number of errors encountered by the drive, even if corrected internally, often signal problems developing with the drive. The trend is in some cases more important than the actual count.
- Spin-Up Time: Changes in spin-up time can reflect problems with the spindle motor.
- Temperature: Increases in drive temperature often signal spindle motor problems.
- Data Throughput: Reduction in the transfer rate of the drive can signal various internal problems.
In order to use S.M.A.R.T. one must have an IDE hard drive that supports it. Most major manufacturers today produce SMART capable drives. In most cases one's BIOS will support smart, but even if it doesn't there are SMART aware utilities that can monitor these conditions.
The hard drive itself will analyze the SMART conditions and if values fall out of tolerance ranges, or trends are too strong, the drive will flag an alert condition in a SMART status register.
The above list is a direct quote and much of the information comes from:
Kozierok, Charles. The PC Guide, "Self-Monitoring Analysis and Reporting Technology (SMART)," <http://www.pcguide.com/ref/hdd/perf/qual/featuresSMART-c.html>, April 17, 2001.