Seagate ST91000640SS, ST9500621SS Idle Read After Write, Protection Information PI, Levels of PI

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10.7Idle 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.

10.8Protection Information (PI)

Protection Information is intended as a standardized approach to system level LRC traditionally provided by systems using 520 byte formatted LBAs. Drives formatted with PI information provide the same, common LBA count (i.e. same capacity point) as non-PI formatted drives. Sequential performance of a PI drive will be reduced by approximately 1.56% due to the extra overhead of PI being transferred from the media that is not calculated as part of the data transferred to the host. To determine the full transfer rate of a PI drive, transfers should be calculated by adding the 8 extra bytes of PI to the transferred LBA length, i.e. 512 + 8 = 520. PI for- matted drives are physically formatted to 520 byte sectors that store 512 bytes of customer data with 8 bytes of Protection Information appended to it. The advantage of PI is that the Protection Information bits can be man- aged at the HBA and HBA driver level. Allowing a system that typically does not support 520 LBA formats to integrate this level of protection.

Protection Information is valid with any supported LBA size. 512 LBA size is used here as common example.

10.8.1Levels of PI

There are 4 types of Protection Information.

Type 0 - Describes a drive that is not formatted with PI information bytes. This allows for legacy support in non- PI systems.

Type 1 - Provides support of PI protection using 10 and 16 byte commands. The RDPROTECT and WRTPRO- TECT bits allow for checking control through the CDB. Eight bytes of Protection Information are transmitted at LBA boundaries across the interface if RDPROTECT and WRTPROTECT bits are nonzero values. Type 1 does not allow the use of 32 byte commands.

Type 2 - Provides checking control and additional expected fields within the 32 byte CDBs. Eight bytes of Pro- tection Information are transmitted at LBA boundaries across the interface if RDPROTECT and WRTPRO- TECT bits are nonzero values. Type 2 does allow the use of 10 and 16 byte commands with zero values in the RDPROTECT and WRTPROTECT fields. The drive will generate 8 bytes (e.g.0xFFFF) 8 bytes of Protection Information to be stored on the media, but the 8 bytes will not be transferred to the host during a read com- mand.

Type 3 - Seagate products do not support Type 3.

10.8.2Setting and determining the current Type Level

A drive is initialized to a type of PI by using the format command on a PI capable drive. Once a drive is format- ted to a PI Type, it may be queried by a Read Capacity (16) command to report the PI type which it is currently formatted to. PI Types cannot coexist on a single drive. A drive can only be formatted to a single PI Type. It can be changed at anytime to a new Type but requires a low level format which destroys all existing data on the drive. No other vehicle for changing the PI type is provided by the T10 SBC3 specification.

Type 1 PI format CDB command:

04

90 00 00 00 00,

Write Buffer: 00 A0 00 00

Type 2 PI format CDB command:

04

D0 00 00 00 00,

Write Buffer: 00 A0 00 00

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Contents SED Fips 140-2 Models ST91000640SSST91000641SS ST9500620SSST9500621SSST91000642SS ST9500622SS Standard Models Self-Encrypting Drive ModelsRevision history Contents Interface requirements Defect and error managementInstallation About Fips About self-encrypting drivesPage Constellation.2 SAS Product Manual, Rev. H List of Figures Constellation.2 SAS Product Manual, Rev. H Seagate Online Support and Services Seagate Technology support servicesScope Electromagnetic susceptibility Applicable standards and reference documentationStandards Electromagnetic compatibilityKorean KCC Electromagnetic complianceElectromagnetic compliance for the European Union Australian C-TickChina Restriction of Hazardous Substances RoHS Directive European Union Restriction of Hazardous Substances RoHSSelf-Encrypting Drives Reference Manual Reference documentsGeneral description Media description Standard featuresProgrammable drive capacity PerformanceReliability Formatted capacitiesFactory-installed options Access time Performance characteristicsInternal drive characteristics Seek performance characteristicsStart/stop time General performance characteristicsCache operation Prefetch/multi-segmented cache controlPrefetch operation Caching write dataUnrecoverable 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 0Dh Parameter Code DescriptionThermal monitor Implementation State of the drive prior to testingDrive Self Test DST DST failure definitionLog page entries Short and extended testsShort test Function Code 001b Extended test Function Code 010bProduct repair and return information Product warrantyShipping StoragePowerChoiceTM power management Physical/electrical specificationsPowerChoice modes DC power requirements AC power requirements1000GB drive Standard & SED model DC power requirements 500GB drive Standard & SED model DC power requirements Power sequencing General DC power requirement notesConducted noise immunity TB model current profiles Current profilesGB model current profiles 1TB model drive in 3Gb operation Power dissipation1TB model drive in 6Gb operation 500GB model drive in 3Gb operation 500GB model drive in 6Gb operation Environmental limits Temperature a. OperatingRelative humidity Shock and vibration Effective altitude sea level a. OperatingShock Recommended mounting Corrosive environment Air cleanlinessVibration a. Operating-normal AcousticsSee Section Constellation.2 SAS Product Manual, Rev. H Mounting configuration dimensions Mechanical specificationsSeagate Enterprise SED About FipsPurpose Validation ProgramExample of Fips tamper evidence labels Data encryption Controlled accessAdmin SP About self-encrypting drivesData bands Authenticated firmware downloadRandom number generator RNG Drive lockingSupported commands Power requirementsDrive internal defects/errors Defect and error managementDrive error recovery procedures SAS system errors Media Pre-Scan Background Media ScanDeferred Auto-Reallocation Levels of PI Setting and determining the current Type LevelIdle Read After Write Protection Information PIIdentifying a Protection Information drive Drive orientation InstallationAir flow CoolingGrounding Drive mountingInterface requirements SAS featuresDual port support Supported commands Scsi commands supportedSupported commands Supported commands Supported commands Inquiry data Mode Sense dataConstellation.2 inquiry data Page Block Descriptor 00 00 00 00 3a 38 60 30 00 00 00 00 00 00 02 Miscellaneous features Miscellaneous operating features and conditionsMiscellaneous status SAS physical interface Datum B Section C C Section a a Pin descriptions Physical characteristicsConnector requirements Electrical descriptionReady LED Out Signal characteristicsPower SAS transmitters and receiversGeneral interface characteristics SAS-2 Specification ComplianceLED drive signal Differential signalsNumerics IndexKCC Msid Mtbf See also cooling Page Constellation.2 SAS Product Manual, Rev. H Page Americas Seagate Technology LLC
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