Attribute Values; Attribute Thresholds; Threshold Exceeded Condition; Smart Commands - Hitachi HDS723020BLA642 Specifications

9.5

SMART Function

The intent of Self-monitoring, analysis and reporting technology (SMART) 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, SMART 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.
9.5.1 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.
9.5.2

Attribute values

Attribute values are used to represent the relative reliability of individual performance or calibration attributes.
The valid range of attribute values is from 1 to 253 decimal. Higher attribute values indicate that the analysis
algorithms being used by the device are predicting a lower probability of a degrading or faulty 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 faulty condition existing.
9.5.3

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 values 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.
9.5.4

Threshold exceeded condition

If one or more attribute values, whose Pre-failure bit of their status flag is set, are less than or equal to their
corresponding attribute thresholds, then the device reliability status is negative, indicating an impending
degrading or faulty condition.
9.5.5

SMART commands

The SMART commands provide access to attribute values, attribute thresholds and other logging and reporting
information.
Hitachi hard disk drive specifications
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