Seagate ST300MM0026, ST9600204FC, ST9450404FC 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.

38	Savvio 10K.4 FC Product Manual, Rev. A

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Contents Savvio 10K.4 FC ST9600204FC ST9450404FCRevision history Rev. a 03/26/10 Initial releaseContents Installation Seagate Technology support services Savvio 10K.4 FC Product Manual, Rev. a Scope Standards, compliance and reference documents StandardsElectromagnetic compatibility Electromagnetic susceptibilityEuropean Union Restriction of Hazardous Substances RoHS Reference documents Ncits TR-19General description Standard features Media descriptionFormatted capacities PerformanceReliability Programmable drive capacity Factory-installed optionsUser-installed accessories Performance characteristics Internal drive characteristicsAccess time Seek performanceFormat command execution time minutes General performance characteristicsStart/stop time Prefetch/multi-segmented cache controlCache operation Caching write data Prefetch operationReliability specifications Error ratesRecoverable Errors Unrecoverable ErrorsReliability and service Seek errorsInterface errors Preventive maintenancePerformance impact 4 S.M.A.R.TControlling S.M.A.R.T Reporting control Determining ratePredictive failures Thermal monitorState of the drive prior to testing Temperature Log Page 0DhDrive Self Test DST DST failure definitionInvoking DST Short and extended testsShort test Function Code 001b Extended test Function Code 010bProduct warranty AbortPowerChoice modes Physical/electrical specificationsPowerChoiceTM power management AC power requirements DC power requirements DC power requirements for ST9600204FC model 2Gb 4Gb AmpsDC power requirements for ST9450404FC model 2Gb 4Gb Amps Conducted noise immunity General DC power requirement notesPower sequencing Current profiles Savvio 10K.4 FC Product Manual, Rev. a Power dissipation ST9600204FCST9450404FC Relative humidity Temperature a. OperatingEnvironmental limits Shock Effective altitude sea level a. OperatingShock and vibration Package size Packaged/product weight Drop height Recommended mountingAir cleanliness Vibration a. Operating-normalAcoustics Corrosive environmentChina Restriction of Hazardous Substances RoHS Directive Mechanical specifications Mounting configuration dimensionsDrive 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 WriteInstallation Drive ID/option selectionDrive orientation CoolingDrive mounting Air flowGrounding FC-AL features Fibre Channel link service framesLink services supported Type of frame 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 BytesFibre Channel port login accept Fibre Channel Process LoginNPort Login Accept ACC payload Bytes Process Login Plri payloadFibre Channel Process Login Accept Fibre Channel fabric loginProcess Login Accept ACC payload Bytes Fabric Login Flogi payload BytesFibre Channel fabric accept login Fabric Login Accept ACC payload BytesDual port support Fibre Channel Arbitrated Loop optionsFC-AL options supported Option SupportedScsi commands supported Supported commands Command code Command nameVerify error recovery page 07h Savvio 10K.4 FC Product Manual, Rev. a Temperature page 0Dh Savvio 10K.4 FC inquiry data Bytes Data hex Mode Sense dataInquiry data Page Mode Data Header 34 65 f8 70 00 00 02 Miscellaneous operating features and conditions Supported Feature or conditionPhysical description Physical characteristicsFC-AL physical interface Pin descriptions Connector requirementsElectrical description FC-SCA pin descriptions Pin Signal name Signal type FC-AL transmitters and receiversPower Fault LED OutMotor start controls Enable port bypass signalsActive LED Out Parallel Enclosure Services Interface ESI 11 SEL6 through SEL0 ID linesAlpa SEL ID 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 Web Seagate Technology support servicesWarranty Support Direct.seagate.com Spp.seagate.com Technical Support Warranty Service Data Recovery Services Authorized Service CentersData Recovery Services Call Center Toll-free Direct dial Presales SupportSavvio 10K.4 FC Product Manual, Rev. a Index FCP Flogi Plogi Page See also cooling Page Seagate Technology LLC