K6602743
Rev.2
02.12.’02
- 56 -
6.3.2.8 SMART Feature
The intent of self-monitoring, analysis, and reporting technology (SMART) is to protect user data and
minimize the likelihood of 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, SMART
devices attempt to predict the likelihood of near-term degradation or fault condition. Providing the host
system the knowledge of a negative reliability condition, allows the host system to warn the user of the
impending risk of a data loss and advise the user of appropriate action. Support of this feature set is
indicated in bit 0 of word 82 of the Identify Device response.
The SMART commands use a single command code and are differentiated by the value placed in the
Features register. The commands supported by this feature set are:
−
SMART Enable Operations
−
SMART Disable Operations
−
SMART Return Status
−
SMART Enable/Disable Attribute AUTOSAVE
−
SMART Save Attribute Values
−
SMART Enable/Disable Automatic Off-line
−
SMART Execute Off-line Immediate
−
SMART Read Log Sector
−
SMART Write Log Sector
6.3.2.8.1 Attribute Parameters
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 fault conditions for that particular device. The specific set of attributes being used
and the identity of these attributes is vendor specific and proprietary.
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.
Each attribute value has a corresponding attribute threshold limit that is used for direct comparison to the
attribute value to indicate the existence of a degrading or fault condition. The device manufacturer through
design and reliability testing and analysis determine the numerical values of the attribute thresholds. 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.
If one or more attribute values are less than or equal to their corresponding attribute thresholds, then the
device reliability status indicates an impending degrading or fault condition.
