Self-Monitoring, Analysis, And Reporting Technology

S.M.A.R.T. is an attempt to predict imminent drive failure by monitoring selected drive performance and calibration characteristics. Each monitored characteristic (Attribute) is used to calculate an Attribute Value. Attribute Values range from 1 to 253 with 1 being worst case, 253 being best case, and 100 being nominal.

For WD drives, the normalized attribute value will range from 1 to 100 or 1 to 200, depending on the attribute. Error rate, total spin ups, spin up retries and calibration retries attributes are implemented as during normal operation (“on-line”); whereas, Multi-zone Error Rate test is performed “off-line”. This test performs a read-verify-all operation and calculates an error rate. These Attributes are updated and stored on the drive in the reserved area of the disk. Also stored on the drive is a set of Attribute Thresholds that correspond to the calculated Attribute Values. An impending degrading or faulty condition is indicated when the calculated Attribute Value becomes less than or equal to its corresponding Attribute Threshold value.

The drive periodically saves all data associated with the S.M.A.R.T. feature. The data is written to the reserved area of the disk after certain time of inactivity by the host. The save of the data is performed in the background and will not cause a decrease in performance.

SMART Attribute Information

Each SMART attribute indicates a certain characteristic of the drive and has its own value derived from a special normalization algorithm and formula. The attributes listed below are specific to WD drives. Other drive manufacturers may have their own attribute definition.

RAW Read Error Rate	This attribute indicates the average rate of read error retries.
Spin Up Time	This attribute indicates the average spin up time, which describes amount of time it took to spin the platters up to their rated rotation speed.
Start/Stop Count	This attribute indicates the amount of drive's start/stop cycles.
Reallocated Sector Count	The attribute indicates the amount of bad sectors relocated to a spare area.
Seek Error Rate	This attribute indicates the average rate of seek errors.
Power On Hour Count	This attribute indicates how long the drive was working (powered on).
Spin Retry Count	This attribute indicates the number of retry of drive spin up at power up.
Calibration Retry Count	This attribute indicates the number of retry of drive calibration after spin up.
Power Cycle Count	This attribute indicates the number of disk power cycles.
Relocation Event Count	This attribute indicates the number of times recalibration was requested.
Current Pending Sector Count	This attribute indicates the amount of sectors pending for relocation. Sectors with read or write errors are recorded and await relocations to spare sectors when next write commands are issued.
Off-line Scan Uncorrectable Sector Count	This attribute indicates the number of firmware uncorrectable error sectors detected during the last off-line scan.
UltraDMA CRC Error Rate	UDMA controller performs a CRC error checking on data while transferring between the host and HDD. Each time the error occurs, a retransmission is requested. This attribute indicates the average rate of the CRC errors.
Multi Zone Error Rate	This attribute indicates a rate at which write retries are requested.
GMR Head Amp	This attribute indicates the amplitude of GMR (Giant Magnetoresistive) head.
Temperature	This attribute indicates the temperature for drives equipped with thermal sensor.