Seagate ST31000426SS, ST31000425SS manual Prefetch/multi-segmented cache control, Cache operation

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5.4Prefetch/multi-segmented cache control

The drive provides a prefetch (read look-ahead) and multi-segmented cache control algorithms that in many cases can enhance system performance. Cache refers to the drive buffer storage space when it is used in cache operations. To select this feature, the host sends the Mode Select command with the proper values in the applicable bytes in page 08h. Prefetch and cache operations are independent features from the standpoint that each is enabled and disabled independently using the Mode Select command; however, in actual opera- tion, the prefetch feature overlaps cache operation somewhat as described in sections 5.5.1 and 5.5.2.

All default cache and prefetch mode parameter values (Mode Page 08h) for standard OEM versions of this drive family are given in Table 10.

5.5Cache operation

Note. Refer to the SAS Interface Manual for more detail concerning the cache bits.

Of the 16MB physical buffer space in the drive, approximately 13,000 kbytes can be used as a cache. The buf- fer is divided into logical segments from which data is read and to which data is written.

The drive keeps track of the logical block addresses of the data stored in each segment of the buffer. If the cache is enabled (see RCD bit in the SAS Interface Manual), data requested by the host with a read command is retrieved from the buffer, if possible, before any disc access is initiated. If cache operation is not enabled, the buffer is still used, but only as circular buffer segments during disc medium read operations (disregarding Prefetch operation for the moment). That is, the drive does not check in the buffer segments for the requested read data, but goes directly to the medium to retrieve it. The retrieved data merely passes through some buffer segment on the way to the host. All data transfers to the host are in accordance with buffer-full ratio rules. See the explanation provided with the information about Mode Page 02h (disconnect/reconnect control) in the SAS Interface Manual.

The following is a simplified description of the prefetch/cache operation:

Case A—read command is received and all of the requested logical blocks are already in the cache: 1. Drive transfers the requested logical blocks to the initiator.

Case B—A Read command requests data, and at least one requested logical block is not in any segment of the cache:

1.The drive fetches the requested logical blocks from the disc and transfers them into a segment, and then from there to the host in accordance with the Mode Select Disconnect/Reconnect parameters, page 02h.

2.If the prefetch feature is enabled, refer to section 5.5.2 for operation from this point.

Each cache segment is actually a self-contained circular buffer whose length is an integer number of logical blocks. The drive dynamically creates and removes segments based on the workload. The wrap-around capa- bility of the individual segments greatly enhances the cache’s overall performance.

Note. The size of each segment is not reported by Mode Sense command page 08h, bytes 14 and 15. The value 0XFFFF is always reported regardless of the actual size of the segment. Sending a size specification using the Mode Select command (bytes 14 and 15) does not set up a new segment size. If the STRICT bit in Mode page 00h (byte 2, bit 1) is set to one, the drive responds as it does for any attempt to change an unchangeable parameter.

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Constellation ES Series SAS Product Manual, Rev. E

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Contents SED Fips 140-2 Models ST32000446SS ST31000426SS ST3500416SSStandard Models Self-Encrypting Drive Models Revision history Contents Defect and error management InstallationAbout Fips About self-encrypting drives Interface requirementsPower Constellation ES Series SAS Product Manual, Rev. E List of Figures Constellation ES Series SAS Product Manual, Rev. E Seagate Technology support services Seagate Online Support and ServicesScope Applicable standards and reference documentation StandardsElectromagnetic compatibility Electromagnetic susceptibilityElectromagnetic compliance Electromagnetic compliance for the European UnionAustralian C-Tick Korean KCCReference documents European Union Restriction of Hazardous Substances RoHSGeneral description Standard features Media descriptionPerformance ReliabilityFormatted capacities Programmable drive capacityFactory-installed options Performance characteristics Internal drive characteristicsSeek performance characteristics Access timeGeneral performance characteristics Start/stop timePrefetch/multi-segmented cache control Cache operationCaching write data Prefetch operationReliability specifications Error ratesRecoverable Errors Unrecoverable ErrorsReliability and service Seek errorsInterface errors Preventive maintenance4 S.M.A.R.T Controlling S.M.A.R.TPerformance impact Reporting controlThermal monitor Temperature Log Page 0Dh Parameter Code DescriptionPredictive failures State of the drive prior to testing Drive Self Test DSTDST failure definition ImplementationShort and extended tests Short test Function Code 001bExtended test Function Code 010b Log page entriesProduct repair and return information Product warrantyShipping PowerChoice modes Physical/electrical specificationsPowerChoiceTM power management AC power requirements DC power requirementsConstellation ES Series SAS Product Manual, Rev. E Constellation ES Series SAS Product Manual, Rev. E Page Conducted noise immunity General DC power requirement notesPower sequencing Current profiles TB model current profilesConstellation ES Series SAS Product Manual, Rev. E GB model current profiles Power dissipation 2TB models in 3Gb operation2TB models in 6Gb operation 1TB models in 3Gb operation 1TB models in 6Gb operation Os per Second ST3500414SS CURRENT/POWER vs Throughput SAS 3.0GB500GB models in 3Gb operation 500GB models in 6Gb operation Relative humidity Temperature a. OperatingEnvironmental limits Shock Effective altitude sea level a. OperatingShock and vibration Recommended mounting Air cleanliness Vibration a. Operating-normalAcoustics Corrosive environmentElectromagnetic susceptibility Mechanical specifications Mounting configuration dimensionsLevel 2 security About FipsPurpose Controlled access Admin SPAbout self-encrypting drives Data encryptionDefault password Random number generator RNGDrive locking Data bandsAuthenticated firmware download Power requirementsSupported commands Cryptographic eraseDrive error recovery procedures Defect and error managementDrive internal defects/errors SAS system errors Deferred Auto-Reallocation Background Media ScanMedia Pre-Scan Idle Read After Write Installation Drive orientationCooling Air flowDrive mounting GroundingSAS features Interface requirementsDual port support Scsi commands supported Supported commandsSupported commands Supported commands Supported commands Constellation ES inquiry data Mode Sense dataInquiry 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 status Miscellaneous operating features and conditionsMiscellaneous features SAS physical interface Datum B Section C C Section a a Physical characteristics Connector requirementsElectrical description Pin descriptionsSignal characteristics PowerSAS transmitters and receivers Ready LED OutSAS-2 Specification Compliance LED drive signalDifferential signals General interface characteristicsIndex NumericsKCC Msid Mtbf See also cooling Page Constellation ES Series SAS Product Manual, Rev. E Page Seagate Technology LLC

ST3500414SS, ST3500415SS, ST32000445SS, ST31000425SS, ST32000446SS specifications

Seagate, a leader in data storage solutions, has introduced a range of high-capacity and reliable hard drives designed for enterprise environments, including the Seagate ST31000424SS, ST3500416SS, ST31000426SS, ST32000444SS, and ST32000446SS. Each of these models is built with an emphasis on performance, endurance, and advanced data protection technologies, catering to mission-critical applications and data-intensive workloads.

The ST31000424SS is a 1TB drive designed for servers and data centers. It offers a 7,200 RPM spindle speed and a 6 Gb/s SATA interface, ensuring quick data access and transfer rates. With a 64MB cache buffer, the ST31000424SS provides enhanced read/write performance, making it suitable for applications that demand quick responses from the storage subsystem.

Similarly, the ST3500416SS is a high-capacity 500GB model, also spinning at 7,200 RPM with a 6 Gb/s SATA interface. This drive is ideal for mid-range servers and enterprise storage, providing an excellent balance of performance and capacity for users looking to optimize their storage efficiency while maintaining lower power consumption.

The ST31000426SS expands the capacity to 1TB while retaining the same reliability and performance characteristics as its counterparts. Its robust design ensures reliability in multi-drive environments, making it an appealing choice for virtualization and database applications, where performance is critical.

The ST32000444SS and ST32000446SS represent Seagate's commitment to higher capacities, with both offering 2TB of storage. They both feature 7,200 RPM speeds, 6 Gb/s SATA interfaces, and 64MB cache buffers, catering to high-demand environments such as cloud storage and data analytics. The drives also integrate advanced error recovery and data integrity features, ensuring the protection of sensitive data, which is vital for enterprise users.

Each model supports Seagate's PowerChoice technology, which optimizes power consumption without sacrificing performance, enhancing energy efficiency in modern data centers. With a broad range of capacities and performance levels, these Seagate drives provide scalable solutions tailored to meet the robust demands of today’s enterprise applications, ensuring reliability and performance for critical data operations.
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