S.M.A.R.T. is a system that enables the PC to predict the future failure of devices such as disk drives. Armed with a failure prediction, the user or system manager can back up key data, replace a suspect device prior to data loss, or avoid undesired downtime. S.M.A.R.T. is a key component of improving data integrity and data availability of the PC.
Some history behind S.M.A.R.T. S.M.A.R.T. goes by a variety of names in the computer industry;
- Predictive Failure Analysis (PFA): The name given to S.M.A.R.T. technology by its inventor IBM. PFA is implemented into all of IBM’s mainframe computer systems.
- Drive Failure Prediction (DFP):
The name given to S.M.A.R.T. technology by the first company to implement S.M.A.R.T – Compaq Computer.
Standardization of S.M.A.R.T.
The initial Compaq Computer S.M.A.R.T. specification was modified and submitted for general industry consideration to the Small Form Factor Committee. S.M.A.R.T is now being standardized by ANSI in ATA-4 (ANSI X3T13 ATA\ATAPI-4).
Implementation of S.M.A.R.T.
To implement S.M.A.R.T. the host computer must have a device driver in the BIOS and/or application software that is capable of sending SMART commands to and from the ATA interface registers. All current Maxtor drives are S.M.A.R.T. ready.
S.M.A.R.T. FOR THE AVERAGE PC USER
Over the course of the last several months, most hard drive manufacturers have initiated an industry wide Working Group (which now includes nearly every major storage manufacturer and storage software developer) to insure that SMART is introduced into the general PC industry with good customer satisfaction. The primary goal of the SMART Working Group is to insure that disk drive purchasers are happy with SMART and find it easy to use. The SMART working group also wanted to insure that SMART software and hardware components across the industry remain compatible.
The SMART Working Group has produced a specification called the SMART Application Guide that controls how SMART applications and BIOS’s are implemented. A copy of this specification is available as document number 8055 from the Small Form Factors Standards Committee. The SMART Application Guide makes SMART technology a valuable tool for the average PC user.
In an effort to improve failure prediction accuracy, leading storage manufacturers have recently specified extensions to the SMART industry standard for hard disk drives (document SFF 8035r2). These extension are referred to as OFF-LINE SMART commands, and are expected to one day become known as SMART phase-II. The off-line commands give hard drive manufacturers the opportunity to implement more advanced prediction algorithms for identifying failure modes in storage devices and thus, improve failure prediction accuracy and customer satisfaction.
SMART Off-Line failure prediction diagnostics may take several seconds or even minutes to run and therefore should only be initiated when the hard drive is not servicing user I/O requests. There are two different techniques, or commands, for executing Off-Line Diagnostics. The first technique is “Off-Line Immediate” which starts a single off-line failure prediction diagnostic run in the drive upon command receipt. The second technique is “Off-line” automatic which regularly schedules failure prediction diagnostic to runs at timed intervals when I/O activity to the drive is quiet. Upon completion of any failure prediction diagnostic run, the firmware permanently records updated SMART failure prediction information on the drive. If a user I/O request is received by the device while running an Off-line diagnostic, the diagnostic is terminated within two seconds such that the I/O request may complete in a timely fashion.
The commands for running SMART on drive devices are described below for reference.
S.M.A.R.T. Command Set
The Self-Monitoring Analysis and Reporting Technology (S.M.A.R.T.) command has been implemented to improve the data integrity and data availability of hard disk drives. In some cases, a S.M.A.R.T. capable device will predict an impending failure with sufficient time to allow users to backup their data and replace the drive before data loss or loss of service.
The S.M.A.R.T. sub-commands (listed below) comprise the ATA S.M.A.R.T. feature set that provide access to S.M.A.R.T. attribute values, attribute thresholds and other logging and reporting information.
Prior to writing a S.M.A.R.T. command to the device’s command register, key values must be written by the host into the device’s Cylinder Low and Cylinder High registers, or the command will be aborted. For any S.M.A.R.T. sub-command, if a device register is not specified as being written with a value by the host, then the value in that register is undefined and will be ignored by the device. The key values are:
|4Fh||Cylinder Low (1F4h)|
|C2h||Cylinder High (1F5h)|
The S.M.A.R.T. sub-commands use a single command code (B0h) and are differentiated from one another by the value placed in the Features register. In order to issue a command, the host must write the sub-command-specific code to the device’s Features register before writing the command code to the command register. The sub-commands and their respective codes are:
|D0h||S.M.A.R.T. Read Attribute Value
This feature returns 512 bytes of attribute information to the host.
|D1h||S.M.A.R.T. Read Attribute Thresholds
This feature returns 512 bytes of warranty failure thresholds to the host.
To enable this feature, set the sector count register to F1h (enable) or 0 (disable). Attribute values are automatically saved to non-volatile storage on the device after five minutes of idle time and before entering idle, sleep or standby modes. This feature is defaulted to “enabled” when S.M.A.R.T. is enabled via the S.M.A.R.T. Enable Operations commands. The autosave feature will not impact host system performance and does not need to be disabled.
|D3h||S.M.A.R.T. Save Attribute Value
This feature saves the current attribute values to non-volatile storage.
|D4h||Perform Off-Line Data Collection
Data is collected from random seeks, timed pattern seek times and head margin tests.
|DAh||S.M.A.R.T. Return Status
This feature allows the host to assess the status of a S.M.A.R.T. capable device by comparing all saved attribute values with their corresponding warranty failure thresholds. If no thresholds are exceeded, the drive is declared to have a positive health status. If any warranty failure threshold is exceeded, the drive is declared to have a negative health status. Executing this sub-command results in all attribute values being saved to non-volatile storage on the device.
|DBh||Enable/Disable Automatic Off-Line
To enable this feature, set the Sector Count register to F1h or 0 to disable
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It is expected that SMART technology will in a few years find its way onto every PC system desktop, be a routine subject of conversation at user group meetings, and be a key step in making the PC a truly friendly information appliance.
StorageSoft, Inc. ® provides a commercial S.M.A.R.T. Utility: