Seagate ST31000640SSIM manual SAS system errors, Background Media Scan, Media Pre-Scan

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7.3SAS system errors

Information on the reporting of operational errors or faults across the interface is given in the SAS Interface Manual. The SSP Response returns information to the host about numerous kinds of errors or faults. The Receive Diagnostic Results reports the results of diagnostic operations performed by the drive.

Status returned by the drive to the initiator is described in the SAS Interface Manual. Status reporting plays a role in systems error management and its use in that respect is described in sections where the various com- mands are discussed.

7.4Background Media Scan

Background Media Scan (BMS) is a self-initiated media scan. BMS is defined in the T10 document SPC-4 available from the T10 committee. BMS performs sequential reads across the entire pack of the media while the drive is idle. In RAID arrays, BMS allows hot spare drives to be scanned for defects prior to being put into service by the host system. On regular duty drives, if the host system makes use of the BMS Log Page, it can avoid placing data in suspect locations on the media. Unreadable and recovered error sites will be logged or reallocated per ARRE/AWRE settings.

With BMS, the host system can consume less power and system overhead by only checking BMS status and results rather than tying up the bus and consuming power in the process of host-initiated media scanning activ- ity.

Since the background scan functions are only done during idle periods, BMS causes a negligible impact to sys- tem performance. The first BMS scan for a newly manufactured drive is performed as quickly as possible to verify the media and protect data by setting the “Start time after idle” to 5ms, all subsequent scans begin after 500ms of idle time. Other features that normally use idle time to function will function normally because BMS functions for bursts of 800ms and then suspends activity for 100ms to allow other background functions to operate.

BMS interrupts immediately to service host commands from the interface bus while performing reads. BMS will complete any BMS-initiated error recovery prior to returning to service host-initiated commands. Overhead associated with a return to host-servicing activity from BMS only impacts the first command that interrupted BMS, this results in a typical delay of about 1 ms.

7.5Media Pre-Scan

Media Pre-Scan is a feature that allows the drive to repair media errors that would otherwise have been found by the host system during critical data accesses early in the drive’s life. The default setting for Media Pre-Scan is enabled on standard products. Media Pre-Scan checks each write command to determine if the destination LBAs have been scanned by BMS. If the LBAs have been verified, the drive proceeds with the normal write command. If the LBAs have not been verified by BMS, Pre-Scan will convert the write to a write verify to certify that the data was properly written to the disk.

Note. During Pre-Scan write verify commands, write performance may decrease by 50% until Pre-Scan completes. Write performance testing should be performed after Pre-Scan is complete. This may be checked by reading the BMS status.

To expedite the scan of the full pack and subsequently exit from the Pre-Scan period, BMS will begin scanning immediately when the drive goes to idle during the Pre-Scan period. In the event that the drive is in a high transaction traffic environment and is unable to complete a BMS scan within 24 power on hours BMS will dis- able Pre-Scan to restore full performance to the system.

Barracuda ES.2 SAS Product Manual, Rev. G

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Contents ST31000640SS ST3750630SS ST3500620SS Barracuda ES.2 SASPage General description Performance characteristicsReliability specifications Physical/electrical specificationsInstallation Defect and error managementInterface requirements Seagate Technology Support Services Barracuda ES.2 SAS Product Manual, Rev Scope Barracuda ES.2 SAS Product Manual, Rev. G Electromagnetic susceptibility Standards, compliance and reference documentsStandards Electromagnetic compatibilityCompliance Reference documents Barracuda ES.2 SAS Product Manual, Rev. G Barracuda ES.2 drive illustration General descriptionReliability Standard featuresMedia description PerformanceFormatted capacities Factory-installed optionsProgrammable drive capacity Barracuda ES.2 SAS Product Manual, Rev. G Seek performance Performance characteristicsInternal drive characteristics Access timeGeneral performance characteristics Format command execution time minutesStart/stop time Cache operation Prefetch/multi-segmented cache controlCaching write data Prefetch operation Unrecoverable Errors Reliability specificationsError rates Recoverable ErrorsPreventive maintenance Reliability and serviceSeek errors Interface errorsReporting control 4 S.M.A.R.TControlling S.M.A.R.T Performance impactPredictive failures Temperature Log Page 0DhThermal monitor Invoking DST State of the drive prior to testingDST failure definition ImplementationLog page entries Product warrantyShort test Function Code 001b Extended test Function Code 010bProduct repair and return information ShippingBarracuda ES.2 SAS Product Manual, Rev. G ST31000640SS DC power requirements Physical/electrical specificationsAC power requirements DC power requirementsST3500620SS DC power requirements ST3750630SS DC power requirementsCurrent profiles General DC power requirement notesPower sequencing Conducted noise immunityTypical ST31000640SS drive +5V and +12V current profiles Typical ST3500620SS drive +5V and +12V current profiles Power dissipationBarracuda ES.2 SAS Product Manual, Rev. G Environmental limits Temperature a. OperatingShock Relative humidityEffective altitude sea level a. Operating Shock and vibrationPackage size Packaged/product weight Drop height Corrosive environment Air cleanlinessVibration a. Operating-normal AcousticsSee Section Barracuda ES.2 SAS Product Manual, Rev. G Physical dimensions Mechanical specificationsDrive internal defects/errors Defect and error managementDrive error recovery procedures 108.29 Background Media Scan SAS system errorsMedia Pre-Scan Idle Read After Write Deferred Auto-ReallocationDrive orientation InstallationAir flow CoolingGrounding Drive mountingBarracuda ES.2 SAS Product Manual, Rev. G Interface requirements SAS featuresDual port support Commands supported by Barracuda ES.2 SAS family drives Scsi commands supportedCommand name Command code Supported Commands supported by Barracuda ES.2 SAS family drives Commands supported by Barracuda ES.2 SAS family drives Commands supported by Barracuda ES.2 SAS family drives Inquiry data Mode Sense dataBarracuda ES.2 SAS inquiry data Bytes Data hex Page Mode Pages 2.1 ST31000640SS Mode Sense data2.2 ST3750630SS Mode Sense data 2.3 ST3500620SS Mode Sense data Miscellaneous status Miscellaneous operating features and conditionsMiscellaneous features Supported Feature or conditionSAS physical interface Datum B Connector requirements Physical characteristicsSAS pin descriptions Pin Signal name Signal typeElectrical description Pin descriptionsReady LED Out Signal characteristicsPower SAS transmitters and receiversEye masks Eye masks overview LED drive signalDifferential signals General interface characteristicsNormalized time in UI Receive eye maskJitter tolerance masks Absolute amplitudeFrequency in kHz Peak-toSinusoidal JitterSignal characteristica Units Gbps Transmitter signal characteristicsGbps m, n Deterministic jitterq Receiver signal characteristicsSignal characteristic Units Gbps Maximum allowable jitterImpedance requirements Sheet 1 Impedance specificationsReceiver jitter tolerance Compliant jitter test pattern CjtpatImpedance requirements Sheet 2 Transmitter characteristicsElectrical TxRx connections = -5,437dB Shows the zero-length test load Receiver characteristics Barracuda ES.2 SAS Product Manual, Rev. G
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