Seagate ST3500071FC, ST3400071FC manual

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To enable Prefetch, use Mode Select page 08h, byte 12, bit 5 (Disable Read Ahead—DRA bit). DRA bit = 0 enables prefetch.

Since data that is prefetched replaces data already in some buffer segments, the host can limit the amount of prefetch data to optimize system performance. The Max Prefetch field (bytes 8 and 9) limits the amount of prefetch. The drive does not use the Prefetch Ceiling field (bytes 10 and 11).

During a prefetch operation, the drive crosses a cylinder boundary to fetch more data only if Mode parameters page 08h, byte 2, bit 4 is set to 1 (Discontinuity—DISC bit).

When prefetch (read look-ahead) is enabled (enabled by DRA = 0), it operates under the control of ARLA (Adaptive Read Look-Ahead). If the host uses software interleave, ARLA enables prefetch of contiguous blocks from the disc when it senses that a prefetch hit will likely occur, even if two consecutive read operations were not for physically contiguous blocks of data (e.g. “software interleave”). ARLA disables prefetch when it decides that a prefetch hit will not likely occur. If the host is not using software interleave, and if two sequential read operations are not for contiguous blocks of data, ARLA disables prefetch, but as long as sequential read operations request contiguous blocks of data, ARLA keeps prefetch enabled.

4.5.3Optimizing cache performance for desktop and server applications

Desktop and server applications require different drive caching operations for optimal performance. This means it is difficult to provide a single configuration that meets both of these needs. In a desktop environment, you want to configure the cache to respond quickly to repetitive accesses of multiple small segments of data without taking the time to “look ahead” to the next contiguous segments of data. In a server environment, you want to configure the cache to provide large volumes of sequential data in a non-repetitive manner. In this case, the ability of the cache to “look ahead” to the next contiguous segments of sequential data is a good thing.

The Performance Mode (PM) bit controls the way the drive switches the cache buffer into different modes of segmentation. In “server mode” (PM bit = 0), the drive can dynamically change the number of cache buffer segments as needed to optimize the performance, based on the command stream from the host. In “desktop mode” (PM bit = 1), the number of segments is maintained at the value defined in Mode Page 8, Byte 13, at all times. For additional information about the PM bit, refer to the Unit Attention Parameters page (00h) of the Mode Sense command (1Ah) in the Fibre Channel Interface Product Manual, part number 77767496.

NL35 Series FC Product Manual, Rev. D

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Contents ST3500071FC ST3400071FC NL35 Series FCPage Contents Interface requirements Defect and error managementInstallation Seagate Technology support services NL35 Series FC Product Manual, Rev. D NL35 Series family disc drive List of FiguresViii NL35 Series FC Product Manual, Rev. D NL35 Series family disc drive ScopeNL35 Series FC Product Manual, Rev. D Electromagnetic susceptibility Applicable standards and reference documentationStandards Electromagnetic compatibilityEnvironmental protection Electromagnetic complianceFibre Channel Interface Manual Reference documentsNL35 Series FC Product Manual, Rev. D General description Standard features Formatted capacities Media descriptionPerformance ReliabilityProgrammable drive capacity Factory-installed accessoriesFactory-installed options User-installed accessoriesAccess time Performance characteristicsInternal drive characteristics Seek performance characteristicsGHz Generalized performance characteristicsCache operation Start/stop timePrefetch/multi-segmented cache control Prefetch operation Caching write dataPage NL35 Series FC Product Manual, Rev. D Error rates Reliability specificationsSeek errors Reliability and serviceRecoverable Errors Unrecoverable errorsHot plugging the drive Preventive maintenanceMean Time Between Failure Mtbf Milliseconds 4 S.M.A.R.TControlling S.M.A.R.T Performance impactParameter Code Description Temperature Log page 0DhPredictive failures Thermal monitorImplementation State of the drive prior to testingDrive Self Test DST DST Failure DefinitionExtended test Function Code 010b Invoking DSTShort and extended tests Short test Function Code 001bProduct repair and return information Product warrantyAbort ShippingST3500071FC/ST3400071FC DC power requirements Physical/electrical specificationsAC power requirements DC power requirementsConducted noise immunity General DC power requirement notesPower sequencing Power dissipation Effective altitude sea level TemperatureEnvironmental limits Relative humidityShock Package size Packaged/product weight Drop heightShock and vibration Recommended mounting Vibration Air cleanlinessAcoustics Typical idle mode sound power ST3500071FC and ST3400071FCCorrosive environment Mounting configuration dimensions Mechanical specificationsNL35 Series FC Product Manual, Rev. D Drive error recovery procedures Defect and error managementDrive internal defects/errors 108.3 Media Pre-Scan FC-AL system errorsBackground Media Scan NL35 Series FC Product Manual, Rev. D Drive orientation InstallationDrive ID/option selection Air flow CoolingGrounding Drive mountingNL35 Series FC Product Manual, Rev. D Type of frame Link service FC-AL featuresFibre Channel link service frames Link services supportedFC Scsi FCP response codes Fibre Channel task management functionsFibre Channel Scsi FCP task management functions Fibre Channel task management responsesBytes Fibre Channel port loginNPort login Plogi payload Process Login Plri payload Fibre Channel port login acceptNPort Login Accept ACC payload Fibre Channel Process LoginFabric Login Flogi payload Fibre Channel Process Login AcceptProcess Login Accept ACC payload Fibre Channel fabric loginFabric Login Accept ACC payload Fibre Channel fabric accept loginOption Supported Dual port supportFibre Channel Arbitrated Loop options FC-AL options supportedCommand code Supported Command name Scsi commands supportedSupported commands Supported commands Supported commands Supported commands Supported commands Bytes Data hex Mode Sense dataInquiry data NL35 Series inquiry dataPage DEF CHG NL35 Series FC Product Manual, Rev. D Miscellaneous status Miscellaneous operating features and conditionsMiscellaneous features Supported Feature or conditionPhysical description Physical characteristicsFC-AL physical interface Electrical description Connector requirementsPart description Positions Part number Features FC-SCA pin descriptions Pin Signal name Signal typePin descriptions FC-AL transmitters and receivers PowerFault LED Out Active LED Out conditions Enable port bypass signalsNormal command activity LED status Active LED Out11 SEL6 through SEL0 ID lines Motor start control signalsParallel Enclosure Services Interface ESI Motor start controlsHex Dec SettingArbitrated loop physical address Alpa values Signal characteristics Differential Pecl input characteristics LED driver signalsLED drive signal Differential Pecl output characteristicsLink rate GHz Eye diagram data valuesNL35 Series FC Product Manual, Rev. D Technical Support Seagate Technology support servicesInternet Presales SupportData Recovery Services Call Center Toll-free Direct dial Warranty ServiceData Recovery Services Authorized Service Centers Numerics IndexFAN Flogi Plogi Page See also cooling
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