GFDL:SMART

Self-Monitoring, Analysis, and Reporting Technology, or S.M.A.R.T., is a monitoring system for computer hard disks to detect and report on various indicators of reliability, in the hope of anticipating failures.

Working modality
Fundamentally, hard drives can suffer one of two classes of failures:
 * Predictable ones, when some failure modes, especially mechanical wear and aging, happen gradually over time. A monitoring device can detect these, much as a temperature dial on the dashboard of an automobile can warn a driver &mdash; before serious damage occurs &mdash; that the engine has started to overheat.
 * Unpredictable ones, when other failures may occur suddenly and unpredictably, such as an electronic component burning out.

Monitoring a drive's behavior can predict approximately 60 percent of hard drive failures. S.M.A.R.T. has the purpose of warning a user or system administrator of impending drive failure while time remains to take preventive action &mdash; such as copying the data to a replacement device.

Compaq pioneered S.M.A.R.T., but most major hard-drive and motherboard vendors now support it to some extent. Many motherboards will display a warning message when a disk drive approaches failure. However, at the present time S.M.A.R.T. is not implemented correctly on many computer platforms due to the absence of industry-wide software & hardware standards for S.M.A.R.T. data interchange.

From a legal perspective, the term "S.M.A.R.T." refers only to a signaling method between internal disk drive electromechanical sensors and the host computer--thus a disk drive manufacturer could include a sensor for just one physical attribute and then advertise the product as S.M.A.R.T. compatible. For example, some drive manufacturers claim to support S.M.A.R.T. but do not include a temperature sensor. In the case of electronic devices, reliability is typically the inverse of temperature, so temperature can be a crucial predictor of failure.

During periods of heavy usage (such as "defrag" operations, or in the case of a web-server) internal drive temperature can exceed the manufacturer's published specifications. Damage to electronics from excessive temperature is cumulative. A S.M.A.R.T.-compliant temperature sensor can warn the operator before a disk drive is damaged by excessive heat, but this sensor is frequently omitted by manufacturers. With regard to disk drives in particular, the term "S.M.A.R.T." is therefore a virtually-meaningless standard because many drive manufacturers claim to support it but simultaneously refuse to disclose which physical characteristics are monitored by onboard sensors. This creates confusion and prevents the consumer from making valid comparisons.

Some disk controllers can duplicate all write operations on a secondary "backup" drive in real-time. This feature is known as "R.A.I.D. mirroring." However, many programs which are designed to analyze changes in drive behavior and relay S.M.A.R.T. alerts to the operator do not function when a computer system is configured for R.A.I.D. support. Additionally, some S.M.A.R.T.-enabled motherboards and related software may not communicate with certain S.M.A.R.T.-capable drives, depending on the type of interface (e.g. SCSI, Fibre channel, IDE, SATA, SAS, SSA). On the Windows platform, many programs designed to monitor and report S.M.A.R.T. information will only function under an administrator account. It is probable that the computer industry will correctly implement S.M.A.R.T. only when a significant percentage of consumers demand compatibility, standardization, and full-disclosure from manufacturers.

Attributes
Each drive manufacturer defines a set of attributes and selects threshold values which attributes should not go below under normal operation. Attribute values can range from 1 to 253 (1 representing the worst case and 253 representing the best). Depending on the manufacturer, a value of 100 or 200 will often be chosen as the "normal" value. Manufacturers that have supported one or more S.M.A.R.T. attributes in various products include: Samsung, Seagate, IBM (Hitachi), Fujitsu, Maxtor, WD (Western Digital). These manufacturers do not necessarily agree on precise attribute definitions and measurement units; therefore the following list should be regarded as a general reference only.

Known S.M.A.R.T. attributes
(Attributes marked "CRITICAL" are potential indicators of imminent electromechanical failure)

Software
Various operating-system specific software can extend the users ability to monitor disk drive conditions through the S.M.A.R.T. interface and predict when a failure is likely to occur by logging deviations in attribute values. This software may also possess the capability to distinguish between gradual degradation over time (representing normal wear) and a sudden change (which may indicate a more serious problem).


 * Zbigniew Chlondowski; Interesting links to several SMART tools in the downloads section.
 * smartmontools &mdash; open-source for Windows, Linux, FreeBSD, NetBSD, OpenBSD, Solaris, Darwin and OS/2
 * DiskView &mdash; sharewAre for Windows. Integrates with Windows Explorer
 * DriveSitter &mdash; shareware for Windows
 * HDDlife &mdash; shareware for Windows
 * DiskCheckup &mdash; free personal use for Windows.
 * SMART Disk Monitor &mdash; shareware for Windows, Linux & Unix
 * ActiveSMART &mdash; shareware for Windows
 * HDD Health &mdash; freeware for Windows
 * SMARTReporter &mdash; open-source for Apple Macintosh
 * S.M.A.R.T. &mdash; commercial software for Apple Macintosh
 * SpeedFan&mdash; Excellent monitoring utility; freeware for Windows
 * HD Tune&mdash; freeware for Windows