Self-Monitoring, Analysis and Reporting Technology

provided failure prediction by monitoring certain online hard drive activities.

A subsequent version of the standard improved failure prediction by adding an automatic off-line read scan to monitor additional operations.

technology not only monitors hard drive activities but adds failure prevention by attempting to detect and repair sector errors.

Also, while earlier versions of the technology only monitored hard drive activity for data that was retrieved by the operating system, this latest S.M.A.R.T.

It was measuring several key device health parameters and evaluating them within the drive firmware.

Communications between the physical unit and the monitoring software were limited to a binary result: namely, either "device is OK" or "drive is likely to fail soon".

Each disk drive vendor was free to decide which parameters were to be included for monitoring, and what their thresholds should be.

Compaq submitted IntelliSafe to the Small Form Factor (SFF) committee for standardization in early 1995.

[13] It was supported by IBM, by Compaq's development partners Seagate, Quantum, and Conner, and by Western Digital, which did not have a failure prediction system at the time.

[14] The resulting jointly developed standard was named S.M.A.R.T.. That SFF standard described a communication protocol for an ATA host to use and control monitoring and analysis in a hard disk drive, but did not specify any particular metrics or analysis methods.

specification by the Small Form Factor (SFF) Committee were added to ATA-3,[16] published in 1997.

The predicted failure may be catastrophic or may be something as subtle as the inability to write to certain sectors, or perhaps slower performance than the manufacturer's declared minimum.

Many motherboards display a warning message upon boot when a disk drive is approaching failure.

refers only to a signaling method between internal disk drive electromechanical sensors and the host computer.

implementations still differ and in some cases may lack "common" or expected features such as a temperature sensor or only include a few select attributes while still allowing the manufacturer to advertise the product as "S.M.A.R.T.

With so many ways to connect a hard drive (SCSI, Fibre Channel, ATA, SATA, SAS, SSA, NVMe and so on), it is difficult to predict whether S.M.A.R.T.

Even with a hard drive and interface that implements the specification, the computer's operating system may not see the S.M.A.R.T.

Instead, one of the following occurs:[29] In any case, the vendor field, also commonly called a "raw value", may be displayed as a decimal or hexadecimal number; its meaning is entirely up to the drive manufacturer (but often corresponds to counts or a physical unit, such as degrees Celsius or seconds).

attribute in various products include Samsung, Seagate, IBM (Hitachi), Fujitsu, Maxtor, Toshiba, Intel, sTec, Inc., Western Digital and ExcelStor Technology.

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.

Drives do not support all attribute codes (sometimes abbreviated as "ID", for "identifier", in tables).

Some codes are specific to particular drive types (magnetic platter, flash, SSD).

"[43] On some pre-2005 drives, this raw value may advance erratically and/or "wrap around" (reset to zero periodically).

[44] For some HDDs it might be stored as a unsigned 16-bit integer[citation needed], which would cause it to wrap around after 65535.

[50] If the value drops to 0 the device may become read-only to allow the user to retrieve stored data.

[53] (HDD, Advanced Format) Number of user data accesses (both reads and writes) where LBAs are not 4 KiB aligned (LBA % 8 != 0) or where size is not modulus 4 KiB (block count != 8), assuming logical block size (LBS)=512 B (indicating bad software configuration).

[68][69] Operating systems often access the file system a few times a minute in the background,[70] causing 100 or more load cycles per hour if the heads unload: the load cycle rating may be exceeded in less than a year.

except in one place, but the equivalent logging/failure-prediction functionality is available in standard log pages prescribed by SPC-4.

[20] Information related to the reallocation of bad sectors is provided not via a log page, but via the READ DEFECT DATA command.

In addition to a grand total, this command provides information about which specific sectors were allocated and why.