Overall (general) throughput performance of a hard disk drive. If the value of this attribute is deceasing there is a high probability of troubles with your disk.

Average time of spindle spin up (from zero RPM (Revolutions Per Minute) to fully operational). Active SMART shows the raw value of this attribute in milliseconds or seconds.

This raw value of this attribute is a count of hard disk spindle start/stop cycles.

Count of reallocated sectors. When the hard drive finds a read/write/verification error, it marks this sector as "reallocated" and transfers data to a special reserved area (spare area).
This process is also known as remapping and "reallocated" sectors are called remaps. This is why, on a modern hard disks, you can not see "bad blocks" while testing the surface - all bad blocks are hidden in reallocated sectors. However, the more sectors that are reallocated, the more a sudden decrease (up to 10% and more) can be noticed in the disk read/write speed.

Rate of seek errors of the magnetic heads. If there is a failure in the mechanical positioning system, a servo damage or a thermal widening of the hard disk, seek errors arise. More seek errors indicates a worsening condition of a disk surface and the disk mechanical subsystem.

Average performance of seek operations of the magnetic heads. If this attribute is decreasing, it is a sign of problems in the hard disk drive mechanical subsystem.

Count of hours in power-on state. The raw value of this attribute shows total count of hours (or minutes, or seconds, depending on manufacturer) in power-on state. A decrease of this attribute value to the critical level (threshold) indicates a decrease of the MTBF (Mean Time Between Failures).
However, in reality, even if the MTBF value falls to zero, it does not mean that the MTBF resource is completely exhausted and the drive will not function normally.

Count of retry of spin start attempts. This attribute stores a total count of the spin start attempts to reach the fully operational speed (under the condition that the first attempt was unsuccessful). A decrease of this attribute value is a sign of problems in the hard disk mechanical subsystem.

This attribute indicates the number of times recalibration was requested (under the condition that the first attempt was unsuccessful). A decrease of this attribute value is a sign of problems in the hard disk mechanical subsystem.

This attribute indicates the count of full hard disk power on/off cycles.

一時的な読み込みエラーの発生率
通常は再読込されて正常なデータがディスクから読み出される。

This is the rate of "program" read errors occurring when reading data from a disk surface.

soft error :
A soft error is also a signal or datum which is wrong, but is not assumed to imply such a mistake or breakage. After observing a soft error, there is no implication that the system is any less reliable than before.

If detected, a soft error may be corrected by rewriting correct data in place of erroneous data. Highly reliable systems use error correction to correct soft errors on the fly.

Count of remap operations (transfering data from a bad sector to a special reserved disk area - spare area).
The raw value of this attribute shows the total number of attempts to transfer data from reallocated sectors to a spare area. Unsuccessful attempts are counted as well as successful.

Current count of unstable sectors (waiting for remapping). The raw value of this attribute indicates the total number of sectors waiting for remapping. Later, when some of these sectors are read successfully, the value is decreased. If errors still occur when reading some sector, the hard drive will try to restore the data, transfer it to the reserved disk area (spare area) and mark this sector as remapped. If this attribute value remains at zero, it indicates that the quality of the corresponding surface area is low.

Quantity of uncorrectable errors. The raw value of this attribute indicates the total number of uncorrectable errors when reading/writing a sector. A rise in the value of this attribute indicates that there are evident defects of the disk surface and/or there are problems in the hard disk drive mechanical subsystem.

The total quantity of CRC errors during UltraDMA mode. The raw value of this attribute indicates the number of errors found during data transfer in UltraDMA mode by ICRC (Interface CRC).

Write data errors rate. This attribute indicates the total number of errors found when writing a sector. The higher the raw value, the worse the disk surface condition and/or mechanical subsystem is.

Shift of disks towards spindle. The raw value of this attribute indicates how much the disk has shifted. Unit measure is unknown.
NOTE: Shift of disks is possible as a result of a strong shock or a fall, or for other reasons.

Loading on magnetic heads actuator caused by the general operating time. Only time when the actuator was in the operating position is counted.

Loading on magnetic heads actuator caused by numerous recurrences of operations like: reading, recording, positioning of heads, etc. Only the time when heads were in the operating position is counted.

Loading on magnetic heads actuator caused by friction in mechanical parts of the store. Only the time when heads were in the operating position is counted.

Total time of loading on the magnetic heads actuator. This attribute indicates total time in which the drive was under load (on the assumption that the magnetic heads were in operating mode and out of the parking area).

Count of efforts of the rotating moment of a drive.

This attribute shows a count of the number of times the drive was powered down.

Amplitude of heads trembling (GMR-head) in running mode.