| Critical device status attributes |
| Reallocated sectors count | Indicates how many defective sectors were discovered on the drive and remapped using a spare sectors pool. Low values in absence of other fault indications point to the disk surface problem. Raw value indicates the exact number of such sectors. |
| Current pending sectors count | Indicates how many suspected defective sectors are pending "investigation". These will not necessarily be remapped. In fact, such sectors my be not defective at all (e.g. if some transient condition prevented reading of the sector, it will be marked "pending") - they will be then re-tested by the device off-line scan1 procedure and returned to the pool of serviceable sectors. Raw value indicates the exact number of such sectors. |
| Off-line uncorrectable sectors count | Similar to "Reallocated sectors count". Indicates how many defective sectors were found during the off-line scan1. |
| Read error rate | Logs rate at which specified events (errors) occur. Lower value indicates more events (errors). Retries are not necessarily indicate a persistent problem, but one should proceed with caution if any of these attributes is degraded. |
| Read error retry rate |
| Write error rate |
| Seek error rate |
| Recalibration retries | Indicates how often the drive is unable to recalibrate at the first attempt. Raw value may show the exact number of recalibration events (at least with some vendors) but this should be taken with a grain of salt. |
| Spin up time | Low value indicates that a drive takes longer than expected to spin up to its rated speed. Might indicate either a controller or a spindle bearing problem. |
| Spin retry count | Spin retry event is logged each time the drive was unable to spin its platters up to the rated rotation speed in the due time. Spin-up attempt was aborted and retried. This typically indicates severe controller or bearing problem, but may be sometimes caused by power supply problems. |
| Drive lifetime information |
| Drive start/stop count | These two provide the estimation of the drive wear. Vendor estimates the supposed device lifetime and the number of cycles. The value for these attributes is then computed based on this estimation. The T.E.C. condition with one of these attributes does not necessarily indicate a drive failure, but rather suggests that a drive should be considered unreliable due to the wear and tear. Raw values are typically just the count of events. |
| Power off/retract cycle count |
| Power on hours count | Normalized values are computed similar to the above. Despite what the name suggests, the raw value of the attribute is stored using all sorts of measurement units (hours, half-hours, or ten-minute intervals to name a few) depending on the manufacturer of the device. |
| Head flying hours count |
| Operating conditions information |
| Temperature | Indicates the device temperature, if the appropriate sensor is fitted. Lowest byte of the raw value contains the exact temperature value (Celsius degrees). |
| Ultra DMA CRC error rate | Low value of this attribute typically indicates that something is wrong with the connectors and/or cables. Disk-to-host transfers are protected by CRC error detection code when Ultra-DMA 66 or 100 is used. So if the data gets garbled between the disk and the host machine, the receiving controller senses this and the retransmission is initiated. Such a situation is called "UDMA CRC error". Once the problem is rectified (typically by replacing a cable), the attribute value returns to the normal levels pretty quick. |
| G-sense error rate | Indicates if the errors are occurring attributed to the drive shocking (either due to the environmental factors or due to improper installation). The hard drive must be fitted with the appropriate sensor to get information about the G-loads. This attribute is mainly limited to the notebook (2.5") drives. Once the operation conditions are corrected, the attribute value will return to normal. |