Attributes are being used to retrieve current psychical/logical state of a drive and to show their meaning in much more readable form for end-user.

Each attribute can have a certain collection of flags:
  • Pre-failure warranty attribute (PW) - indicates a pre-failure condition (caused by exceeded threshold) where imminent loss of data is being predicted
  • Online collection attribute (OC) - indicates that the value of this attribute is calculated during Online test
  • Performance attribute (PE) - indicates degradation of performance caused by usage or age of a drive
  • Error rate attribute (ER) - indicates that attribute measure frequency of errors
  • Error count attribute (EC) - indicates that attribute is a counter of events
  • Self-preserving attribute (SP) - indicates that attribute is automatically preservable and restored each time when performing S.M.A.R.T. tests

Threshold is the worst value for attribute. Any value lower than (or equal to) threshold means decreased performance or even hard disk failure.

ID Name of attribute Description
1 Raw Read Error RateFrequency of errors appearance while reading RAW data from a disk
2 Throughput PerformanceThe average efficiency of hard disk
3 Spin Up TimeTime needed by spindle to spin-up
4 Start/Stop CountNumber of start/stop cycles of spindle
5 Reallocated Sector CountQuantity of remapped sectors
6 Read Channel MarginReserve of channel while reading
7 Seek Error RateFrequency of errors appearance while positioning
8 Seek Time PerformanceThe average efficiency of operations while positioning
9 Power-On Hours CountQuantity of elapsed hours in the switched-on state
10 Spin-up Retry CountNumber of attempts to start a spindle of a disk
11 Calibration Retry CountNumber of attempts to calibrate a drive
12 Power Cycle CountNumber of complete start/stop cycles of hard disk
13 Soft Read Error RateFrequency of "program" errors appearance while reading data from a disk
191 G-Sense Error RateFrequency of mistakes appearance as a result of impact loads
192 Power-Off Retract CycleNumber of the fixed 'turning off drive' cycles (Fujitsu: Emergency Retract Cycle Count)
193 Load/Unload Cycle CountNumber of cycles into Landing Zone position
194 HDA TemperatureTemperature of a Hard Disk Assembly
195 Hardware ECC RecoveredFrequency of the on the fly errors (Fujitsu: ECC On The Fly Count)
196 Reallocated Event CountQuantity of remapping operations
197 Current Pending Sector CountCurrent quantity of unstable sectors (waiting for remapping)
198 Off-line Scan Uncorrectable CountQuantity of uncorrected errors
199 UltraDMA CRC Error RateTotal quantity of errors CRC during UltraDMA mode
200 Write Error Rate
Frequency of errors appearance while recording data into disk (Western Digital: Multi Zone Error Rate)
201 Soft Read Error RateFrequency of the off track errors (Maxtor: Off Track Errors)
202 Data Address Mark ErrorsFrequency of the Data Address Mark errors
203 Run Out CancelFrequency of the ECC errors (Maxtor: ECC Errors)
204 Soft ECC CorrectionQuantity of errors corrected by software ECC
205 Thermal Asperity RateFrequency of the thermal asperity errors
206 Flying HeightThe height of the disk heads above the disk surface
207 Spin High CurrentQuantity of used high current to spin up drive
208 Spin Buzz Quantity of used buzz routines to spin up drive
209 Offline Seek PerformanceDrive's seek performance during offline operations
220 Disk Shift Shift of disk is possible as a result of strong shock loading in the store, as a result of it's falling or for other reasons (sometimes: Temperature)
221 G-Sense Error RateThis attribute is an indication of shock-sensitive sensor - total quantity of errors appearance as a result of impact loads (dropping drive, for example)
222 Loaded HoursLoading on drive caused by the general operating time of hours it stores
223 Load/Unload Retry CountLoading on drive caused by numerous recurrences of operations like: reading, recording, positioning of heads, etc.
224 Load FrictionLoading on drive caused by friction in mechanical parts of the store
225 Load/Unload Cycle CountTotal of cycles of loading on drive
226 Load-in TimeGeneral time of loading for drive
227 Torque Amplification CountQuantity efforts of the rotating moment of a drive
228 Power-Off Retract CountQuantity of the fixed turning off's a drive
230 GMR Head AmplitudeAmplitude of heads trembling (GMR-head) in running mode
231 TemperatureTemperature of a drive
240 Head Flying HoursTime while head is positioning
250 Read Error Retry RateFrequency of errors appearance while reading data from a disk

Please note that some disk manufacturers use their own ID's for attributes.
Thanks to Bruce Allen for attributes and descriptions.