Hard Drive Diagnostics.
Computer hard drives have an inherent on board application program that reports various non fatal errors to the user or the operating system. This monitoring application is referred to as S.M.A.R.T (Self-Monitoring, Analysis, and Reporting Technology. SMART gathers and records the hard drive's operating characteristics, such as operating temperature, spin-up time, data error rates, etc.
An increase in SMART error reports over a defined period time IS a fair indication that the hard drive environment is not satisfactory or the hard drive performance is not optimum and that the user needs to assess and remedy the reported anomalies or risk a catastrophic failure of the device and the loss of the data written to the device.
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A large number of the SMART reports are Manufacturer specific and also specific to the type and design of the device. detailed information regarding the error reports can be found on the manufacturers web sites. However here is a small example of the many reports available from SMART.
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.
05 0x05 Reallocated Sectors Count
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. 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.
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.
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.
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.
191 0xBF G-sense Error Rate
The count of errors resulting from externally induced shock & vibration.
194 0xC2 Temperature resp. Temperature Celsius
Current internal temperature.
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. 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.