Seagate ST2000NM0063 4 S.M.A.R.T, Controlling S.M.A.R.T, Performance impact, Reporting control

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5.2.4S.M.A.R.T.

S.M.A.R.T. is an acronym for Self-Monitoring Analysis and Reporting Technology. This technology is intended to recognize conditions that indicate imminent drive failure and is designed to provide sufficient warning of a failure to allow you to back up the data before an actual failure occurs.

Note. The drive’s firmware monitors specific attributes for degradation over time but can’t predict instantaneous drive failures.

Each monitored attribute has been selected to monitor a specific set of failure conditions in the operating performance of the drive and the thresholds are optimized to minimize “false” and “failed” predictions.

Controlling S.M.A.R.T.

The operating mode of S.M.A.R.T. is controlled by the DEXCPT and PERF bits on the Informational Exceptions Control mode page (1Ch). Use the DEXCPT bit to enable or disable the S.M.A.R.T. feature. Setting the DEXCPT bit disables all S.M.A.R.T. functions. When enabled, S.M.A.R.T. collects on-line data as the drive performs normal read and write operations. When the PERF bit is set, the drive is considered to be in “On-line Mode Only” and will not perform off-line functions.

You can measure off-line attributes and force the drive to save the data by using the Rezero Unit command. Forcing S.M.A.R.T. resets the timer so that the next scheduled interrupt is in one hour.

You can interrogate the drive through the host to determine the time remaining before the next scheduled measurement and data logging process occurs. To accomplish this, issue a Log Sense command to log page 0x3E. This allows you to control when S.M.A.R.T. interruptions occur. Forcing S.M.A.R.T. with the RTZ command resets the timer.

Performance impact

S.M.A.R.T. attribute data is saved to the disk so that the events that caused a predictive failure can be recreated. The drive measures and saves parameters once every one hour subject to an idle period on the drive interfaces. The process of measuring off-line attribute data and saving data to the disk is interruptable. The maximum on-line only processing delay is summarized below:

Table 2

 

 

Maximum processing delay

 

 

On-line only delay

Fully-enabled delay

 

DEXCPT = 0, PERF = 1

DEXCPT = 0, PERF = 0

S.M.A.R.T. delay times

233 ms

560 ms

Reporting control

Reporting is controlled by the MRIE bits in the Informational Exceptions Control mode page (1Ch). An example, if the MRIE is set to one, the firmware will issue to the host an 01-5D00 sense code. The FRU field contains the type of predictive failure that occurred. The error code is preserved through bus resets and power cycles.

Determining rate

S.M.A.R.T. monitors the rate at which errors occur and signals a predictive failure if the rate of degraded errors increases to an unacceptable level. To determine rate, error events are logged and compared to the number of total operations for a given attribute. The interval defines the number of operations over which to measure the rate. The counter that keeps track of the current number of operations is referred to as the Interval Counter.

S.M.A.R.T. measures error rates. All errors for each monitored attribute are recorded. A counter keeps track of the number of errors for the current interval. This counter is referred to as the Failure Counter.

Error rate is the number of errors per operation. The algorithm that S.M.A.R.T. uses to record rates of error is to set thresholds for the number of errors and their interval. If the number of errors exceeds the threshold before the interval expires, the error rate is considered to be unacceptable. If the number of errors does not exceed the threshold before the interval expires, the error rate is considered to be acceptable. In either case, the interval and failure counters are reset and the process starts over.

Predictive failures

S.M.A.R.T. signals predictive failures when the drive is performing unacceptably for a period of time. The firmware keeps a running count of the number of times the error rate for each attribute is unacceptable. To accomplish this, a counter is incremented each time the error rate is unacceptable and decremented (not to exceed zero) whenever the error rate is acceptable. If the counter continually increments such that it reaches the predictive threshold, a predictive failure is signaled. This counter is referred to as the Failure History Counter. There is a separate Failure History Counter for each attribute.

CONSTELLATION ES.1 SAS PRODUCT MANUAL, REV. G

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Contents Constellation ES.1 SAS Document Revision History Contents Installation Inquiry data 11.3.2 Mode Sense data Figures Seagate Technology Support Services Scope Model Number Self-Encrypting Drive SED Fips 140-2 LevelApplicable Standards and Reference Documentation Korean KCC Taiwanese BsmiEuropean Union Restriction of Hazardous Substances RoHS China Restriction of Hazardous Substances RoHS DirectiveSAS Interface Manual General Description Standard Features DDADF508 Performance Characteristics Read Write Average Single trackFull stroke Maximum without verifyGeneral performance characteristics Caching write data Prefetch operationReliability Specifications Recoverable ErrorsUnrecoverable Errors Seek errorsPreventive maintenance Hot plugging the drive4 S.M.A.R.T Controlling S.M.A.R.TPerformance impact Reporting controlThermal monitor Parameter Code DescriptionDrive Self Test DST DST failure definitionState of the drive prior to testing ImplementationInvoking DST Short and extended testsProduct warranty AbortShipping StoragePHYSICAL/ELECTRICAL Specifications 2TB drive Standard & SED model DC power requirements 0Gb mode Amps1TB drive Standard & SED model DC power requirements 500GB drive Standard & SED model DC power requirements Current profiles Power sequencingConducted noise immunity TB model current profiles GB model current profiles Power Dissipation Constellation ES.1 SAS Product MANUAL, REV. G Constellation ES.1 SAS Product MANUAL, REV. G Constellation ES.1 SAS Product MANUAL, REV. G Constellation ES.1 SAS Product MANUAL, REV. G Constellation ES.1 SAS Product MANUAL, REV. G Temperature a. Operating Relative humidityEffective altitude sea level a. Operating Shock and vibrationPackage size Packaged/product weight Drop height ShockAir cleanliness VibrationAcoustics Corrosive environmentWeight maximum Mounting configuration dimensionsSeagate Enterprise SED PurposeValidation Program Admin SP Default passwordAbout SELF-ENCRYPTING Drives Locking SPSanitize Cryptographic Erase Defect and Error Management Drive Internal DEFECTS/ERRORSRead and write retry count maximum recovery times Identifying a Protection Information drive Setting and determining the current Type LevelLevels of PI Installation Physical interfaceX = F 15lb = 67N Interface Requirements Task management functionsSAS task management functions supported Task management responsesSupported commands Command name Command code SupportedSupported commands Supported commands Supported commands Inquiry data Mode Sense data Mode Pages Mode Sense data changeable and default values for 1TB drives Mode Pages Miscellaneous features Supported Feature or conditionMiscellaneous status Supported StatusDatum B Section C C Section a a Physical characteristics Connector requirementsPin Signal name Signal type Electrical descriptionPower SAS transmitters and receiversReady LED Out Ready LED Out conditionsGeneral interface characteristics LED drive signalDifferential signals Index Latency Index SAS Seagate Technology LLC
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