Seagate ST2000NM0041, ST1000NM0001, ST1000NM0021 manual Caching write data, Prefetch operation

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5.5.1Caching write data

Write caching is a write operation by the drive that makes use of a drive buffer storage area where the data to be written to the medium is stored while the drive performs the Write command.

If read caching is enabled (RCD=0), then data written to the medium is retained in the cache to be made avail- able for future read cache hits. The same buffer space and segmentation is used as set up for read functions. The buffer segmentation scheme is set up or changed independently, having nothing to do with the state of RCD. When a write command is issued, if RCD=0, the cache is first checked to see if any logical blocks that are to be written are already stored in the cache from a previous read or write command. If there are, the respective cache segments are cleared. The new data is cached for subsequent Read commands.

If the number of write data logical blocks exceed the size of the segment being written into, when the end of the segment is reached, the data is written into the beginning of the same cache segment, overwriting the data that was written there at the beginning of the operation; however, the drive does not overwrite data that has not yet been written to the medium.

If write caching is enabled (WCE=1), then the drive may return Good status on a write command after the data has been transferred into the cache, but before the data has been written to the medium. If an error occurs while writing the data to the medium, and Good status has already been returned, a deferred error will be gen- erated.

The Synchronize Cache command may be used to force the drive to write all cached write data to the medium. Upon completion of a Synchronize Cache command, all data received from previous write commands will have been written to the medium. Table 10 shows the mode default settings for the drive.

5.5.2Prefetch operation

If the Prefetch feature is enabled, data in contiguous logical blocks on the disk immediately beyond that which was requested by a Read command are retrieved and stored in the buffer for immediate transfer from the buf- fer to the host on subsequent Read commands that request those logical blocks (this is true even if cache operation is disabled). Though the prefetch operation uses the buffer as a cache, finding the requested data in the buffer is a prefetch hit, not a cache operation hit.

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

The drive does not use the Max Prefetch field (bytes 8 and 9) or the Prefetch Ceiling field (bytes 10 and 11).

When prefetch (read look-ahead) is enabled (enabled by DRA = 0), the drive enables prefetch of contiguous blocks from the disk when it senses that a prefetch hit will likely occur. The drive disables prefetch when it decides that a prefetch hit is not likely to occur.

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Contents ST1000NM0041 ST500NM0041 Standard Models Self-Encrypting Drive ModelsSED Fips 140-2 Models ST2000NM0041 Revision history Contents Installation Defect and error managementAbout Fips About self-encrypting drives Interface requirementsPage Constellation ES.1 SAS Product Manual, Rev. E List of Figures Constellation ES.1 SAS Product Manual, Rev. E Seagate Online Support and Services Seagate Technology support servicesModel Number Self-Encrypting Drive SED Fips 140-2 Level ScopeStandards Applicable standards and reference documentationElectromagnetic compatibility Electromagnetic susceptibilityElectromagnetic compliance for the European Union Electromagnetic complianceAustralian C-Tick Korean KCCChina Restriction of Hazardous Substances RoHS Directive European Union Restriction of Hazardous Substances RoHSSelf-Encrypting Drives Reference Manual Reference documentsGeneral description Standard features Media descriptionPerformance Reliability Factory-installed optionsFormatted capacities Programmable drive capacityInternal drive characteristics Performance characteristicsSeek performance characteristics Access timeStart/stop time General performance characteristicsCache operation Prefetch/multi-segmented cache controlPrefetch operation Caching write dataError rates Reliability specificationsRecoverable Errors Unrecoverable ErrorsSeek errors Reliability and serviceInterface errors Preventive maintenanceControlling S.M.A.R.T 4 S.M.A.R.TPerformance impact Reporting controlTemperature Log Page 0Dh Parameter Code Description Predictive failuresThermal monitor Drive Self Test DST State of the drive prior to testingDST failure definition ImplementationShort test Function Code 001b Short and extended testsExtended test Function Code 010b Log page entriesShipping Product warrantyStorage Product repair and return informationPhysical/electrical specifications PowerChoiceTM power managementPowerChoice modes DC power requirements AC power requirementsRegulation ±5% Constellation ES.1 SAS Product Manual, Rev. E Constellation ES.1 SAS Product Manual, Rev. E General DC power requirement notes Power sequencingConducted noise immunity TB model current profiles Current profilesConstellation ES.1 SAS Product Manual, Rev. E GB model current profiles 2TB models in 3Gb operation Power dissipation2TB models in 6Gb operation 1TB models in 3Gb operation 1TB models in 6Gb operation 500GB models in 3Gb operation 500GB models in 6Gb operation Temperature a. Operating Environmental limitsRelative humidity Effective altitude sea level a. Operating Shock and vibrationShock Recommended mounting Vibration a. Operating-normalAir cleanliness AcousticsCorrosive environment Mounting configuration dimensions Mechanical specificationsPurpose About FipsValidation Program Seagate Enterprise SEDExample of Fips tamper evidence labels Admin SP Controlled accessAbout self-encrypting drives Data encryptionRandom number generator RNG Authenticated firmware downloadDrive locking Data bandsSupported commands Power requirementsSanitize Cryptographic Erase RevertSPDefect and error management Drive internal defects/errorsDrive error recovery procedures SAS system errors Background Media Scan Media Pre-ScanDeferred Auto-Reallocation Idle Read After Write Setting and determining the current Type LevelProtection Information PI Levels of 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 Mode Sense data Inquiry dataConstellation ES.1 inquiry data Page Mode Sense data changeable and default values for 2TB drives Mode Sense data changeable and default values for 1TB drives 3a 38 60 30 00 00 02 Miscellaneous operating features and conditions Miscellaneous featuresMiscellaneous status SAS physical interface Datum B Section C C Section a a Connector requirements Physical characteristicsElectrical description Pin descriptionsPower Signal characteristicsSAS transmitters and receivers Ready LED OutLED drive signal SAS-2 Specification ComplianceDifferential signals General interface characteristicsConstellation ES.1 SAS Product Manual, Rev. E Numerics IndexKCC Msid Mtbf See also cooling Page Constellation ES.1 SAS Product Manual, Rev. E Page Americas Seagate Technology LLC

ST2000NM0001, ST1000NM0041, ST500NM0001, ST2000NM0021, ST1000NM0021 specifications

Seagate is a renowned leader in data storage solutions, offering a wide array of hard disk drives (HDDs) suitable for various applications. Among their product lineup, the Seagate ST2000NM0041, ST500NM0021, ST500NM0041, ST1000NM0001, and ST1000NM0021 stand out as reliable options tailored for enterprise environments and general storage needs.

The Seagate ST2000NM0041 is a 2TB 7200 RPM drive designed for high-performance workloads in data centers. One of its key features is the use of the SATA III interface, providing data transfer speeds of up to 6 Gbps, ensuring quick access to data. This model supports advanced error recovery controls and features enhanced power management capabilities, which contribute to its reliable performance and energy efficiency.

Next, the ST500NM0021 and ST500NM0041 are both 500GB drives that cater to different consumer needs. The ST500NM0021 is a 5400 RPM drive, typically used in scenarios where lower power consumption is vital, such as in compact systems or external storage configurations. Its efficient design enables quieter operation, making it ideal for environments that require minimal noise. Conversely, the ST500NM0041 operates at a speed of 7200 RPM, making it suitable for more demanding applications that require swift read and write speeds. Both models utilize Serial ATA for connectivity, ensuring compatibility with a wide range of systems.

The ST1000NM0001 and ST1000NM0021 are 1TB drives that provide versatility across different platforms. Similar to their 500GB counterparts, the ST1000NM0001 features a 7200 RPM speed, optimizing performance for applications requiring faster data processing. In contrast, the ST1000NM0021 operates at 5400 RPM, designed for users prioritizing energy efficiency over speed, like in desktop and external storage solutions. Each of these drives supports advanced technologies such as Native Command Queuing (NCQ), which enhances performance by allowing multiple commands to be executed simultaneously.

Overall, the Seagate ST series hard drives offer flexible storage options for a variety of applications. With their robust features, including varied RPM speeds, power management, and compatibility with SATA connections, these drives cater to the needs of both consumer and enterprise markets, establishing Seagate as a trusted provider in the storage arena.
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