Understanding the SMART Attributes

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The SMART Attributes list in the DiskCheckup "SMART Info" window contains all SMART attributes supported by the currently selected drive. (See What is SMART? for more information)

The Attributes

ID

Name

Raw value is better when*

Description**

1

Raw Read Error Rate

Lower

Represents the rate of uncorrected read errors

2

Throughput Performance

Higher

Represents the throughput performance of the drive. I.e. The speed at which the drive is reading and writing data.

3

Spin Up Time

Lower

Represents the average amount of time required to spin up the drive spindle to operational speed from a stopped state.

4

Start/Stop Count

Lower

Represents the number of start/stop cycles for the drive. The raw value indicates the count of start/stop cycles for the drive. The drive being powered on/off or suspended/woken up are considered as start/stop cycles.

5

Reallocated Sector Count

Lower

Represents the amount of spare sector pool available. Spare sectors are used to replace sectors that became bad for some reason (for instance, if a read error occurs). Therefore the more sectors reallocated, the worse the condition of the drive.

7

Seek Error Rate

Lower

Represents the number of seek errors. Each time the drive attempts a seek operation, but fails to position its head correctly, the seek error rate increases.

8

Seek Time Performance

Higher

Represents how efficiently the drive is performing seek operations. A low value indicates problems with the drive subsystem, for instance the servo responsible for positioning the head.

9

Power On Hours Count

Higher

This is an informative attribute, the raw value of which displays the number of hours the drive has been powered on for.

A

Spin Retry Count

Lower

Represents the number of times a drive fails to spin its spindle up to operation speed on the first attempt.

B

Calibration Retry Count

Higher

Calibration is the act of repositioning the drive read/write head to cylinder 0. This value represents the number of times a calibration has failed on the first attempt.

C

Power Cycle Count

Lower

Informative attribute, the raw value of which represents the number of drive power on/drive power off cycles for the disk.

D

Soft Read Error Rate

Lower

Uncorrected read errors reported to the operating system.

BE

Temperature Difference from 100

Unkown

The exact specification of this attribute is not quite stable. This is what it is known as on Seagate drives whereas it is called Airflow Temperature on Western Digital hard disks. In either case this attribute usually has to do with subtracting the temperature from 100 to give a value that is worse when it is lower.

BF

G-Sense Error Rate

Lower

Frequency of mistakes as a result of impact loads

C0

Power-off Retract Count

Lower

Number of times the heads are loaded off the media. Heads can be unloaded without actually powering off.

C1

Load/Unload Cycle

Lower

Count of load/unload cycles into head landing zone position.

C2

Temperature

Lower

Informative attribute, the raw value of which represents the current temperature in Celsius of the drive.

C3

Hardware ECC Recovered

Higher

Time between ECC-corrected errors.

C4

Reallocation Event Count

Lower

Represents the number of reallocation events, which have taken place. Sometimes multiple sectors are reallocated together – this corresponds to one reallocation event. (See also: Reallocated Sector Count and Current Pending Sector Count).

C5

Current Pending Sector Count

Lower

Represents the number of sectors currently pending reallocation.

C6

Uncorrectable Sector Count

Lower

The total number of uncorrectable errors when reading/writing a sector.

C7

UltraDMA CRC Error Count

Lower

Represents the number of CRC error found in the Ultra DMA high-speed transfer mode. (CRC stands for Cyclic Redundancy Check and is data verification algorithm which uses polynomial checksums).

C8

Write Error Count

Lower

Represents the rate of uncorrected write errors. Lower raw values indicate that there is a problem with either disk surface or read/write heads.

C9

Soft Read Error Rate

Lower

Number of off-track errors.

CA

Data Address Mark errors

Lower

Number of Data Address Mark errors

CB

Run Out Cancel

Lower

Number of ECC errors

CC

Soft ECC Correction

Lower

Number of errors corrected by software ECC.

CD

Thermal asperity rate(TAR)

Lower

Number of thermal asperity errors.

CE

Flying Height

Unknown

Height of heads above the disk surface.

CF

Spin High Current

Unknown

Amount of high current used to spin up the drive.

D0

Spin Buzz

Unknown

Number of buzz routines to spin up the drive

D1

Offline Seek Performance

Unknown

Drive’s seek performance during offline operations

DC

Disk Shift

Lower

Distance the disk has shifted relative to the spindle (usually due to shock).

DD

G-Sense Error Rate

Lower

The number of errors resulting from externally-induced shock & vibration.

DE

Loaded Hours

Lower

Time spent operating under data load (movement of magnetic head armature)

DF

Load/Unload Retry Count

Unknown

Number of times head changes position.

E0

Load Friction

Lower

Resistance caused by friction in mechanical parts while operating.

E1

Load/Unload Cycle Count

Lower

Total number of load cycles

E2

Load 'In'-time

Unknown

Total time of loading on the magnetic heads actuator (time not spent in parking area).

E3

Torque Amplification Count

Unknown

Number of attempts to compensate for platter speed variations

E4

Power-off Retract Count

Lower

The number of times the magnetic armature was retracted automatically as a result of cutting power.

E6

GMR Head Amplitude

Unknown

Amplitude of "thrashing" (distance of repetitive forward/reverse head motion)

E7

Temperature

Unknown

Drive Temperature, unknown units.

F0

Head Flying Hours

Unknown

Time while head is positioning

FA

Read Error Retry Rate

Lower

Number of errors while reading from a disk

*Raw values are an absolute reading of an attribute as reported by the hard disk; what constitutes a high or a low value will differ between attributes and hard disk models. If you are unsure of how to interpret these values it is better to observe the normalized value, see What is SMART? for more information.

**Descriptions for several of the attributes are taken from various sources on the web including wikipedia.org