Seagate Understanding Error Rates and Predictive Failures for Computer Drives
Page 26

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 inter- val 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 firm- ware keeps a running count of the number of times the error rate for each attribute is unacceptable. To accom- plish 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 pre- dictive 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.

6.2.5Thermal monitor

Savvio drives implement a temperature warning system which:

1.Signals the host if the temperature exceeds a value which would threaten the drive.

2.Signals the host if the temperature exceeds a user-specified value.

3.Saves a S.M.A.R.T. data frame on the drive which exceeds the threatening temperature value.

A temperature sensor monitors the drive temperature and issues a warning over the interface when the tem- perature exceeds a set threshold. The temperature is measured at power-up and then at ten-minute intervals after power-up.

The thermal monitor system generates a warning code of 01-0B01 when the temperature exceeds the speci- fied limit in compliance with the SCSI standard. The drive temperature is reported in the FRU code field of mode sense data. You can use this information to determine if the warning is due to the temperature exceeding the drive threatening temperature or the user-specified temperature.

This feature is controlled by the Enable Warning (EWasc) bit, and the reporting mechanism is controlled by the Method of Reporting Informational Exceptions field (MRIE) on the Informational Exceptions Control (IEC) mode page (1Ch).

The current algorithm implements two temperature trip points. The first trip point is set at 68°C which is the maximum temperature limit according to the drive specification. The second trip point is user-selectable using the Log Select command. The reference temperature parameter in the temperature log page (see Table 1) can be used to set this trip point. The default value for this drive is 68°C, however, you can set it to any value in the range of 0 to 68°C. If you specify a temperature greater than 68°C in this field, the temperature is rounded down to 68°C. A sense code is sent to the host to indicate the rounding of the parameter field.

Table 1: Temperature Log Page (0Dh)

Parameter Code

Description

 

 

0000h

Primary Temperature

 

 

0001h

Reference Temperature

 

 

18

Savvio 15K.3 SAS Product Manual, Rev. A

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Contents Standard Models Self-Encrypting Drive Models ST9300653SSST9300553SS ST9146853SSST9146753SSST9300453SS ST9146653SS SED FIPS140-2 ModelsPage Contents About Fips About self-encrypting drives Defect and error managementInstallation Interface requirementsPage Savvio 15K.3 SAS Product Manual, Rev. a List of Figures Page Seagate Technology support services Seagate Online Support and ServicesScope Electromagnetic compatibility Applicable standards and reference documentationStandards Electromagnetic susceptibilityAustralian C-Tick Electromagnetic complianceElectromagnetic compliance for the European Union Korean KCCEuropean Union Restriction of Hazardous Substances RoHS Scsi Commands Reference Manual SAS Interface Manual Reference documentsGeneral description Standard features Media descriptionFormatted capacities PerformanceReliability Factory installed options Programmable drive capacitySeek performance characteristics Performance characteristicsInternal drive characteristics Access timeStart/stop time Format command execution timeGeneral performance characteristics Prefetch/multi-segmented cache control Cache operationCaching write data Prefetch operationRecoverable Errors Reliability specificationsError rates Unrecoverable ErrorsInterface errors Reliability and serviceSeek errors Preventive maintenanceControlling S.M.A.R.T Maximum processing delay4 S.M.A.R.T Performance impactThermal monitor Temperature Log Page 0Dh Parameter Code DescriptionPredictive failures DST failure definition State of the drive prior to testingDrive Self Test DST ImplementationExtended test Function Code 010b Short and extended testsShort test Function Code 001b Log page entriesProduct repair and return information Product warrantyShipping StoragePowerChoice modes Physical/electrical specificationsPowerChoiceTM power management AC power requirements DC power requirements300GB models DC power requirements Regulation146GB models DC power requirements Conducted noise immunity General DC power requirement notesPower sequencing Current profiles Current profile for 300GB modelsCurrent profile for 146GB models 300GB models in 3Gb operation Power dissipation300GB models in 6Gb operation 146GB models in 6Gb operation 146GB models in 3Gb operationRelative humidity Temperature a. OperatingEnvironmental limits Shock Effective altitude sea level a. OperatingShock and vibration Vibration a. Operating-normal Recommended mountingAcoustics Air cleanlinessCorrosive environment Mechanical specifications DimensionsLevel 2 security About FipsPurpose About self-encrypting drives Controlled accessAdmin SP Data encryptionDrive locking Default passwordRandom number generator RNG Data bandsSupported commands Authenticated firmware downloadPower requirements Cryptographic eraseDrive error recovery procedures Defect and error managementDrive internal defects/errors SAS system errors Background Media ScanIdle Read After Write Media Pre-ScanDeferred Auto-Reallocation Levels of PI Setting and determining the current Type LevelProtection Information PI Identifying a Protection Information driveInstallation Drive orientationCooling Air flowDrive mounting GroundingSAS features Interface requirementsDual port support Scsi commands supportedSupported commands Supported commands Supported commands Supported commands Savvio inquiry data Mode Sense dataInquiry data Page Mode Data Header Mode Data Header Miscellaneous status Miscellaneous operating features and conditionsMiscellaneous features SAS physical interface Datum B Section C C Section a a Electrical description Physical characteristicsConnector requirements Pin descriptionsSAS transmitters and receivers Signal characteristicsPower Ready LED OutDifferential signals SAS-2 Specification complianceLED drive signal General interface characteristicsIndex NumericsPage Msid Mtbf See also cooling Page Savvio 15K.3 SAS Product Manual, Rev. a
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