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S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology) is an interface between the BIOS and a computers hard disk. It is a feature of the Enhanced Integrated Drive Electronics (EIDE) technology that controls access to the hard drive. If S.M.A.R.T is enabled when a computer is set up, the BIOS can receive analytical information from the hard drive and determine whether to send the user a warning message about possible future failure of the hard drive.
SMART monitors a set of drive attributes, such as temperature, throughput performance and the number of hours the drive has been powered on. It compares these attributes to a corresponding set of thresholds. If an attribute drops below its threshold, the drive is no longer considered fit for use and should be replaced immediately. Not all attributes are available on all drives, however. It is the responsibility of the drive manufacturer to include SMART support.
A brief description of some SMART terminology follows.
Attribute
An attribute is a particular property of a SMART enabled hard drive. Each attribute contains the following sub properties.
ID
The attribute ID. This is a non-zero positive number in the range 1-255 (0x01-0xFF in hexadecimal).
Description
A text description of the attribute. See "Understanding the SMART Attributes" for an explanation of the various SMART Attributes.
Raw Value
The raw value varies from attribute to attribute, but it generally represents a more meaningful measure of the attribute. It usually shows a count of the number of errors, hours, or times depending on the attribute in question. For instance, for the temperature attribute, it shows the degrees (in Celsius) of the drive.
Status
Provided a status for the attribute. OK means the attribute value is well in the safe zone and FAIL means that a Threshold Exceeding Condition has been detected.
Value
The attribute value is a normalized number measuring the attributes current reliability. The higher this value is, the more reliable the drive is, insofar as this attribute is concerned. For some attributes, this value is normalized between 1 and 100, for others between 1 and 200 and for others still, such as temperature the attribute value is the actual non-normalized temperature in degrees Celsius. When an attribute value falls below that attributes threshold, the drive is no longer operating safely.
Worst
With the exception of temperature, this is the lowest attribute value that has been recorded for this attribute and shows the moment when the attribute was closest to falling below its threshold. For temperature, it is the highest attribute value recorded.
Threshold
If the attribute value drops below that attribute threshold for any drive, a Threshold Exceeding Condition (TEC) has occurred and the drive should be replaced. The threshold is thus a measure of how an attribute can become before the drive is deemed unsafe.
Predicted TEC Date
This is the predicted date and time of the Threshold Exceed Condition (TEC). Prediction is based on the collected TEC data. See "Threshold Exceed Condition prediction" for more info.
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