Seagate ST3300955FC, ST3400755FC manual Deferred Auto-Reallocation, Idle Read After Write

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7.6Deferred Auto-Reallocation

Deferred Auto-Reallocation (DAR) simplifies reallocation algorithms at the system level by allowing the drive to reallocate unreadable locations on a subsequent write command. Sites are marked for DAR during read oper- ations performed by the drive. When a write command is received for an LBA marked for DAR, the auto-reallo- cation process is invoked and attempts to rewrite the data to the original location. If a verification of this rewrite fails, the sector is re-mapped to a spare location.

This is in contrast to the system having to use the Reassign Command to reassign a location that was unread- able and then generate a write command to rewrite the data. DAR is most effective when AWRE and ARRE are enabled—this is the default setting from the Seagate factory. With AWRE and ARRE disabled DAR is unable to reallocate the failing location and will report an error sense code indicating that a write command is being attempted to a previously failing location.

7.7Idle Read After Write

Idle Read After Write (IRAW) utilizes idle time to verify the integrity of recently written data. During idle periods, no active system requests, the drive reads recently written data from the media and compares it to valid write command data resident in the drives data buffer. Any sectors that fail the comparison result in the invocation of a rewrite and auto-reallocation process. The process attempts to rewrite the data to the original location. If a verification of this rewrite fails, the sector is re-mapped to a spare location.

40	Cheetah NS FC Product Manual, Rev. A

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Contents Cheetah NS FC ST3400755FC ST3300955FCPage Cheetah NS FC Product Manual, Rev. a Cheetah NS FC Product Manual, Rev. a Contents Interface requirements Defect and error managementInstallation Seagate Technology support services Cheetah NS FC Product Manual, Rev. a List of Figures Page Scope Cheetah NS FC Product Manual, Rev. a Electromagnetic compatibility Standards, compliance and reference documentsStandards Electromagnetic susceptibilityCompliance Reference documents Ncits TR-19Cheetah NS FC Product Manual, Rev. a General description Standard features Media descriptionFormatted capacities PerformanceReliability Programmable drive capacityFactory-installed options User-installed accessoriesAccess time Performance characteristicsInternal drive characteristics Seek performanceStart/stop time Format command execution time minutesGeneral performance characteristics Caching write data Prefetch/multi-segmented cache controlCache operation Prefetch operation Recoverable Errors Reliability specificationsError rates Unrecoverable ErrorsInterface errors Reliability and serviceSeek errors Preventive maintenancePerformance impact 4 S.M.A.R.TControlling S.M.A.R.T MillisecondsPredictive failures Reporting controlDetermining rate Thermal monitorDrive Self Test DST State of the drive prior to testingParameter Code Description DST failure definitionShort test Function Code 001b Invoking DSTShort and extended tests Extended test Function Code 010bShipping Product warrantyAbort Product repair and return informationCheetah NS FC Product Manual, Rev. a DC power requirements Physical/electrical specificationsAC power requirements DC power requirements for ST3400755FC model Gbit AmpsGeneral DC power requirement notes DC power requirements for ST3300955FC model Gbit AmpsPower sequencing Conducted noise immunityCurrent profiles Cheetah NS FC Product Manual, Rev. a ST3400755FC Power dissipationST3400755 CURRENT/POWER vs Throughput FC 4GB Random 8 Block ReadsST3300955 CURRENT/POWER vs Throughput FC 4GB ST3300955FCRelative humidity TemperatureEnvironmental limits Shock and vibration Package size Packaged/product weight Drop heightEffective altitude sea level ShockRecommended mounting Acoustics Air cleanlinessVibration Corrosive environmentX表示该部件（于同类物品程度上）所含的危险和有毒物质中国RoHS MCV标准所定义的门槛值。 China Restriction of Hazardous Substances RoHS DirectiveMechanical specifications Mounting configuration dimensionsCheetah NS FC Product Manual, Rev. a Drive error recovery procedures Defect and error managementDrive internal defects/errors 77.87 Media Pre-Scan FC-AL system errorsBackground Media Scan Deferred Auto-Reallocation Idle Read After WriteDrive orientation InstallationDrive ID/option selection CoolingDrive mounting Air flowGrounding Cheetah NS FC Product Manual, Rev. a Link services supported Type of frame FC-AL featuresFibre Channel link service frames Interface requirementsFC Scsi FCP response codes Function name Response code Fibre Channel task management functionsFibre Channel task management responses Fibre Channel port login NPort login Plogi payload BytesNPort Login Accept ACC payload Bytes Fibre Channel port login acceptFibre Channel Process Login Process Login Plri payloadProcess Login Accept ACC payload Bytes Fibre Channel Process Login AcceptFibre Channel fabric login Fabric Login Flogi payload BytesFibre Channel fabric accept login Fabric Login Accept ACC payload BytesFC-AL options supported Dual port supportFibre Channel Arbitrated Loop options Option SupportedScsi commands supported Supported commands Command code Command nameVerify error recovery page 07h Cheetah NS FC Product Manual, Rev. a Temperature page 0Dh Cheetah NS FC inquiry data Bytes Data hex Mode Sense dataInquiry data Page Mode Sense 10 Byte Header Data Mode Data Header Supported Feature or condition Miscellaneous operating features and conditionsMiscellaneous features Miscellaneous statusPhysical description Physical characteristicsFC-AL physical interface Pin descriptions Connector requirementsElectrical description FC-AL transmitters and receivers FC-SCA pin descriptions Pin Signal name Signal typePin Signal name Signal type Power Fault LED OutMotor start controls Enable port bypass signalsActive LED Out Parallel Enclosure Services Interface ESI 11 SEL6 through SEL0 ID linesHex Dec SettingArbitrated loop physical address Alpa values Device control codes Signal characteristicsTTL input characteristics FC Differential input LED driver signalsFC Differential output Receive eye diagram Eye diagram data values Link rate GHz Presales Support Seagate Technology support servicesInternet Technical SupportData Recovery Services Call Center Toll-free Direct dial Warranty ServiceData Recovery Services Authorized Service Centers Index NumericsFAN Flogi Plogi SEL ID See also cooling

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