Self-Monitoring, Analysis and Reporting Technology
Self-Monitoring, Analysis, and Reporting Technology or S.M.A.R.T. is a monitoring tool for computer hard disks to see and report on various
indicators of reliability, in the hope of anticipating failures.
There are fundamentally two classes of hard drive failures. Some
failure modes, especially mechanical wear and aging, happen gradually
over time. These can be detected, much as a temperature dial on
the dashboard of an automobile can warn the driver that the engine
is overheating before serious damage occurs. Other failures are
sudden and unpredictable. Approximately 60 percent of hard drive
failures can be predicted by monitoring the drive's behavior.
The goal of S.M.A.R.T. technology is to warn a user or system
administrator of impending drive failure while there is still
time to take preventive action, such as copying the data to a
replacement device.
As an example, here is a list of the S.M.A.R.T attributes that
are monitored by a WDC800JB-00CRA1 80-gigabyte hard drive:
- Raw Read Error Rate
- Spin Up Time
- Start/Stop Count
- Reallocated Sector Count
- Seek Error Rate
- Power On Hours Count
- Spin Retry Count
- Recalibration Retry Count
- Power Cycle Count
- Reallocation Event Count
- Current Pending Sector Count
- Uncorrectable Sector Count
- CRC Error Count
- Write Error Count
Note that drive temperature is not among the parameters reported
by the drive, because it lacks a temperature sensor. Many other
drives do include temperature sensors.
S.M.A.R.T was pioneered by Compaq (which recently merged with HP),
and is now supported by most major hard drive and motherboard vendors.
Most current motherboards will display a warning message when the
disk drive is near failure.
There are also various monitoring programs that can be used to
keep closer track of a disk drive's health. Each disk maker defines
a set of attributes which the controller monitors, and also defines
threshold values for these attributes that should not be reached in
normal operation. Suitable software can keep track of these parameters
over time, in order to extrapolate the current trends and predict when
a "threshold exceeded condition" is likely to occur. Also, the software
can distinguish between gradual degredation over time, representing
normal wear, versus a sudden change which may indicate a problem.
External Links
http://www.pc-king.co.uk/tips3.htm
http://www.charismac.com/Products/smart/smartrelease.html
Hard disk Specification IBM Deskstar 40GV & 75GXP
The website for one S.M.A.R.T. monitoring utility:
http://www.drivehealth.com/smart.html
[To be continued]
