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12.8 S.M.A.R.T. Function
The intent of Self-monitoring, analysis and reporting technology (S.M.A.R.T) is to protect user data
and prevent unscheduled system downtime that may be caused by predictable degradation and/or
fault of the device. By monitoring and storing critical performance and calibration parameters,
S.M.A.R.T devices employ sophisticated data analysis algorithms to predict the likelihood of
near-term degradation or fault condition. By alerting the host system of a negative reliability status
condition, the host system can warn the user of the impending risk of a data loss and advise the user
of appropriate action.
Since S.M.A.R.T. utilizes the internal device microprocessor and other device resources, there may
be some small overhead associated with its operation. However, special care has been taken in the
design of the S.M.A.R.T. algorithms to minimize the impact to host system performance. Actual
impact of S.M.A.R.T. overhead is dependent on the specific device design and the usage patterns of
the host system. To further ensure minimal impact to the user, S.M.A.R.T. capable devices are
shipped from the device manufacturer’s factory with the S.M.A.R.T. feature disabled. S.M.A.R.T.
capable devices can be enabled by the system OEMs at time of system integration or in the field by
aftermarket products.
12.8.1 Attributes
Attributes are the specific performance or calibration parameters that are used in analyzing the
status of the device. Attributes are selected by the device manufacturer based on that attribute’s
ability to contribute to the prediction of degrading or faulty conditions for that particular device. The
specific set of attributes being used and the identity of these attributes is vendor specific and
proprietary.
12.8.2 Attribute values
Attribute values are used to represent the relative reliability of individual performance or
calibration attributes. Higher attribute values indicate that the analysis algorithms being used by
the device are predicting a lower probability of a degrading or fault condition existing. Accordingly,
lower attribute values indicate that the analysis algorithms being used by the device are predicting a
higher probability of a degrading or fault condition existing. There is no implied linear reliability
relationship corresponding to the numerical relationship between different attribute values for any
particular attribute.
12.8.3 Attribute thresholds
Each attribute value has a corresponding attribute threshold limit which is used for direct
comparison to the attribute value to indicate the existence of a degrading or faulty condition. The
numerical value of the attribute thresholds are determined by the device manufacturer through
design and reliability testing and analysis. Each attribute threshold represents the lowest limit to
which its corresponding attribute value can be equal while still retaining a positive reliability status.
Attribute thresholds are set at the device manufacturer’s factory and cannot be changed in the field.
The valid range for attribute thresholds is from 1 through 253 decimal.
12.8.4 Threshold exceeded condition
If one or more attribute values are less than or equal to their corresponding attribute thresholds,
then the device reliability status is negative, indicating an impending degrading or faulty condition.
12.8.5 S.M.A.R.T. commands
The S.M.A.R.T. commands provide access to attribute values, attribute thresholds and other logging
and reporting information.