http://en.wikipedia.org/wiki/Self-Monitoring,_Analysis,_and_Reporting_Technology#ATA_S.M.A.R.T._attributes

Known ATA S.M.A.R.T. attributes

This article may contain original research. Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research may be removed. (September 2007)

The following chart lists some S.M.A.R.T. attributes and the typical meaning of their raw values. Normalized values are always mapped so that higher values are better (with only very rare exceptions such as the "Temperature" attribute on certain Seagate drives[14]), but higher raw attribute values may be better or worse depending on the attribute and manufacturer. For example, the "Reallocated Sectors Count" attribute's normalized value decreases as the count of reallocated sectors increases. In this case, the attribute's raw value will often indicate the actual count of sectors that were reallocated, although vendors are in no way required to adhere to this convention. As manufacturers do not necessarily agree on precise attribute definitions and measurement units, the following list of attributes should be regarded as a general guide only.

Legend

	Higher raw value is better
	Lower raw value is better
Critical: pink colored row	Potential indicators of imminent electromechanical failure

ID	Hex	Attribute name	Better	Description
01	0x01	Read Error Rate		(Vendor specific raw value.) Stores data related to the rate of hardware read errors that occurred when reading data from a disk surface. The raw value has different structure for different vendors and is often not meaningful as a decimal number.
02	0x02	Throughput Performance		Overall (general) throughput performance of a hard disk drive. If the value of this attribute is decreasing there is a high probability that there is a problem with the disk.
03	0x03	Spin-Up Time		Average time of spindle spin up (from zero RPM to fully operational [millisecs]).
04	0x04	Start/Stop Count		A tally of spindle start/stop cycles. The spindle turns on, and hence the count is increased, both when the hard disk is turned on after having before been turned entirely off (disconnected from power source) and when the hard disk returns from having previously been put to sleep mode.[15]
05	0x05	Reallocated Sectors Count		Count of reallocated sectors. When the hard drive finds a read/write/verification error, it marks that 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". The raw value normally represents a count of the bad sectors that have been found and remapped. Thus, the higher the attribute value, the more sectors the drive has had to reallocate. This allows a drive with bad sectors to continue operation; however, a drive which has had any reallocations at all is significantly more likely to fail in the near future.[2] While primarily used as a metric of the life expectancy of the drive, this number also affects performance. As the count of reallocated sectors increases, the read/write speed tends to become worse because the drive head is forced to seek to the reserved area whenever a remap is accessed. If sequential access speed is critical, the remapped sectors can be manually marked as bad blocks in the file system in order to prevent their use.
06	0x06	Read Channel Margin		Margin of a channel while reading data. The function of this attribute is not specified.
07	0x07	Seek Error Rate	N/A	(Vendor specific raw value.) Rate of seek errors of the magnetic heads. If there is a partial failure in the mechanical positioning system, then seek errors will arise. Such a failure may be due to numerous factors, such as damage to a servo, or thermal widening of the hard disk. The raw value has different structure for different vendors and is often not meaningful as a decimal number.
08	0x08	Seek Time Performance		Average performance of seek operations of the magnetic heads. If this attribute is decreasing, it is a sign of problems in the mechanical subsystem.
09	0x09	Power-On Hours (POH)		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.[16] On some pre-2005 drives, this raw value may advance erratically and/or "wrap around" (reset to zero periodically).[17]
10	0x0A	Spin Retry Count		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). An increase of this attribute value is a sign of problems in the hard disk mechanical subsystem.
11	0x0B	Recalibration Retries or Calibration Retry Count		This attribute indicates the count that recalibration was requested (under the condition that the first attempt was unsuccessful). An increase of this attribute value is a sign of problems in the hard disk mechanical subsystem.
12	0x0C	Power Cycle Count		This attribute indicates the count of full hard disk power on/off cycles.
13	0x0D	Soft Read Error Rate		Uncorrected read errors reported to the operating system.
180	0xB4	Unused Reserved Block Count Total		"Pre-Fail" Attribute used at least in HP devices.
183	0xB7	SATA Downshift Error Count		Western Digital and Samsung attribute.
184	0xB8	End-to-End error / IOEDC		This attribute is a part of Hewlett-Packard's SMART IV technology, as well as part of other vendors' IO Error Detection and Correction schemas, and it contains a count of parity errors which occur in the data path to the media via the drive's cache RAM.[18]
185	0xB9	Head Stability		Western Digital attribute.
186	0xBA	Induced Op-Vibration Detection		Western Digital attribute.
187	0xBB	Reported Uncorrectable Errors		The count of errors that could not be recovered using hardware ECC (see attribute 195).
188	0xBC	Command Timeout		The count of aborted operations due to HDD timeout. Normally this attribute value should be equal to zero and if the value is far above zero, then most likely there will be some serious problems with power supply or an oxidized data cable.[19]
189	0xBD	High Fly Writes		HDD producers implement a Fly Height Monitor that attempts to provide additional protections for write operations by detecting when a recording head is flying outside its normal operating range. If an unsafe fly height condition is encountered, the write process is stopped, and the information is rewritten or reallocated to a safe region of the hard drive. This attribute indicates the count of these errors detected over the lifetime of the drive. This feature is implemented in most modern Seagate drives[1] and some of Western Digital’s drives, beginning with the WD Enterprise WDE18300 and WDE9180 Ultra2 SCSI hard drives, and will be included on all future WD Enterprise products.[20]
190	0xBE	Airflow Temperature (WDC) resp. Airflow Temperature Celsius (HP)		Airflow temperature on Western Digital HDs (Same as temp. [C2], but current value is 50 less for some models. Marked as obsolete.)
190	0xBE	Temperature Difference from 100		Value is equal to (100−temp. °C), allowing manufacturer to set a minimum threshold which corresponds to a maximum temperature.
191	0xBF	G-sense Error Rate		The count of errors resulting from externally induced shock & vibration.
192	0xC0	Power-off Retract Count or Emergency Retract Cycle Count (Fujitsu)[21]		Count of times the heads are loaded off the media. Heads can be unloaded without actually powering off.[citation needed]
193	0xC1	Load Cycle Count or Load/Unload Cycle Count (Fujitsu)		Count of load/unload cycles into head landing zone position.[21] The typical lifetime rating for laptop (2.5-in) hard drives is 300,000 to 600,000 load cycles.[22] Some laptop drives are programmed to unload the heads whenever there has not been any activity for about five seconds.[23] Many Linux installations write to the file system a few times a minute in the background.[24] As a result, there may be 100 or more load cycles per hour, and the load cycle rating may be exceeded in less than a year.[25]
194	0xC2	Temperature resp. Temperature Celsius		Current internal temperature.
195	0xC3	Hardware ECC Recovered	N/A	(Vendor specific raw value.) The raw value has different structure for different vendors and is often not meaningful as a decimal number.
196	0xC4	Reallocation Event Count		Count of remap operations. The raw value of this attribute shows the total count of attempts to transfer data from reallocated sectors to a spare area. Both successful & unsuccessful attempts are counted.[26]
197	0xC5	Current Pending Sector Count		Count of "unstable" sectors (waiting to be remapped, because of unrecoverable read errors). If an unstable sector is subsequently read successfully, this value is decreased and the sector is not remapped. Read errors on a sector will not remap the sector immediately (since the correct value cannot be read and so the value to remap is not known, and also it might become readable later); instead, the drive firmware remembers that the sector needs to be remapped, and will remap it the next time it's written.[27] However some drives will not immediately remap such sectors when written; instead the drive will first attempt to write to the problem sector and if the write operation is successful then the sector will be marked good (in this case, the "Reallocation Event Count" (0xC4) will not be increased). This is a serious shortcoming, for if such a drive contains marginal sectors that consistently fail only after some time has passed following a successful write operation, then the drive will never remap these problem sectors.
198	0xC6	Uncorrectable Sector Count or Offline Uncorrectable or Off-Line Scan Uncorrectable Sector Count[21]		The total count of uncorrectable errors when reading/writing a sector. A rise in the value of this attribute indicates defects of the disk surface and/or problems in the mechanical subsystem.
199	0xC7	UltraDMA CRC Error Count		The count of errors in data transfer via the interface cable as determined by ICRC (Interface Cyclic Redundancy Check).
200	0xC8	Multi-Zone Error Rate [28]		The count of errors found when writing a sector. The higher the value, the worse the disk's mechanical condition is.
200	0xC8	Write Error Rate (Fujitsu)		The total count of errors when writing a sector.[29]
201	0xC9	Soft Read Error Rate or TA Counter Detected		Count of off-track errors.
202	0xCA	Data Address Mark errors or TA Counter Increased		Count of Data Address Mark errors (or vendor-specific).[citation needed]
203	0xCB	Run Out Cancel
204	0xCC	Soft ECC Correction		Count of errors corrected by software ECC[citation needed]
205	0xCD	Thermal Asperity Rate (TAR)		Count of errors due to high temperature.[19]
206	0xCE	Flying Height		Height of heads above the disk surface. A flying height that's too low increases the chances of a head crash while a flying height that's too high increases the chances of a read/write error.[citation needed]
207	0xCF	Spin High Current		Amount of surge current used to spin up the drive.[19]
208	0xD0	Spin Buzz		Count of buzz routines needed to spin up the drive due to insufficient power.[19]
209	0xD1	Offline Seek Performance		Drive’s seek performance during its internal tests.[19]
210	0xD2	Vibration During Write		(found in a Maxtor 6B200M0 200GB and Maxtor 2R015H1 15GB disks)
211	0xD3	Vibration During Write		Vibration During Write[citation needed]
212	0xD4	Shock During Write		Shock During Write[citation needed]
220	0xDC	Disk Shift		Distance the disk has shifted relative to the spindle (usually due to shock or temperature). Unit of measure is unknown.
221	0xDD	G-Sense Error Rate		The count of errors resulting from externally induced shock & vibration.
222	0xDE	Loaded Hours		Time spent operating under data load (movement of magnetic head armature)[citation needed]
223	0xDF	Load/Unload Retry Count		Count of times head changes position.[citation needed]
224	0xE0	Load Friction		Resistance caused by friction in mechanical parts while operating.[citation needed]
225	0xE1	Load/Unload Cycle Count		Total count of load cycles[citation needed]
226	0xE2	Load 'In'-time		Total time of loading on the magnetic heads actuator (time not spent in parking area).[citation needed]
227	0xE3	Torque Amplification Count		Count of attempts to compensate for platter speed variations[citation needed]
228	0xE4	Power-Off Retract Cycle		The count of times the magnetic armature was retracted automatically as a result of cutting power.[citation needed]
230	0xE6	GMR Head Amplitude		Amplitude of "thrashing" (distance of repetitive forward/reverse head motion)[citation needed]
230	0xE6	Drive Life Protection Status		Current state of drive operation based upon the Life Curve[30]
231	0xE7	Temperature		Drive Temperature
231	0xE7	SSD Life Left		Indicates the approximate SSD life left, in terms of program/erase cycles or Flash blocks currently available for use.[30]
232	0xE8	Endurance Remaining		Number of physical erase cycles completed on the drive as a percentage of the maximum physical erase cycles the drive is designed to endure
232	0xE8	Available Reserved Space		Intel SSD reports the number of available reserved space as a percentage of reserved space in a brand new SSD.
233	0xE9	Power-On Hours		Number of hours elapsed in the power-on state.
233	0xE9	Media Wearout Indicator		Intel SSD reports a normalized value of 100 (when the SSD is new) and declines to a minimum value of 1. It decreases while the NAND erase cycles increase from 0 to the maximum-rated cycles.
234	0xEA	Average erase count AND Maximum Erase Count		Decoded as: byte 0-1-2 = average erase count (big endian) and byte 3-4-5 = max erase count (big endian)[31]
235	0xEB	Good Block Count AND System(Free) Block Count		decoded as: byte 0-1-2 = good block count (big endian) and byte 3-4 = system(free) block count.
240	0xF0	Head Flying Hours		Time while head is positioning[citation needed]
240	0xF0	Transfer Error Rate (Fujitsu)		Count of times the link is reset during a data transfer.[32]
241	0xF1	Total LBAs Written		Total count of LBAs written
242	0xF2	Total LBAs Read		Total count of LBAs read. Some S.M.A.R.T. utilities will report a negative number for the raw value since in reality it has 48 bits rather than 32.
250	0xFA	Read Error Retry Rate		Count of errors while reading from a disk
254	0xFE	Free Fall Protection		Count of "Free Fall Events" detected [33]

Threshold Exceeds Condition

Threshold Exceeds Condition (TEC) is an estimated date when a critical drive statistic attribute will reach its threshold value. When Drive Health software reports a "Nearest T.E.C.", it should be regarded as a "Failure date". Sometimes, no date is given and the drive can be expected to work without errors.[34]

To predict the date, the drive tracks the rate at which the attribute changes. Note that TEC dates are only estimates; hard drives can and do fail much sooner or much later than the TEC date.[35]