Seagate ST9450405SS, ST9900605SS 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 12.

5.5Cache operation

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

Of the 64MB physical buffer space in the drive, approximately 30,000KB are available as a data cache. The remaining buffer space is reserved for internal drive use.

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.

Savvio 10K.5 SAS Product Manual, Rev. D

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Contents Standard Models Self-Encrypting Drive Models ST9900605SS ST9600005SS ST9450205SS ST9300405SSSED Fips 140-2 Models Revision Date Sheets affected or comments Revision historyContents Interface requirements Defect and error managementInstallation About Fips About self-encrypting drivesPage Savvio 10K.5 SAS Product Manual, Rev. D List of Figures Page Seagate Online Support and Services Seagate Technology support servicesStandard models Standard SED models SED Fips 140-2 models ScopeElectromagnetic 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 Reference documentsGeneral description Media description Standard featuresPerformance Programmable drive capacity Factory-installed optionsReliability Formatted capacitiesAccess 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 StorageMode Description Physical/electrical specificationsPowerChoiceTM power management PowerChoice modesDC power requirements AC power requirements0Gb mode Amps 900GB standard drive DC power requirements600GB standard drive DC power requirements 450GB standard model DC power requirements 300GB standard model DC power requirements Power sequencing General DC power requirement notesConducted noise immunity Current profiles for 900GB models Current profilesCurrent profiles for 600GB models Current profiles for 450GB models Current profiles for 300GB models GB models in 3Gb operation Power dissipation900GB models in 6Gb operation GB models in 3Gb operation 600GB models in 6Gb operation 450GB models in 3Gb operation 450GB models in 6Gb operation 300GB models in 3Gb operation Environmental limits Temperature a. Operating300GB models in 6Gb operation Effective altitude sea level a. Operating Relative humidityShock and vibration Recommended mounting ShockVibration a. Operating-normal Air cleanlinessCorrosive environment Acoustics Mounting configuration dimensions Mechanical specificationsPurpose About FipsLevel 2 security Data encryption Controlled accessAdmin SP About self-encrypting drivesCryptographic erase Random number generator RNGDrive locking Data bandsRevertSP Authenticated firmware downloadPower requirements Supported commandsDrive internal defects/errors Defect and error managementDrive error recovery procedures Background Media Scan SAS system errorsDeferred Auto-Reallocation Media Pre-ScanIdle Read After Write Identifying a Protection Information drive Setting and determining the current Type LevelProtection Information PI Levels of PIPhysical interface InstallationCooling Drive orientationGrounding Drive mountingInterface requirements SAS featuresDual port support Scsi commands supportedSupported commands Command name Command code SupportedSupported commands Supported commands Supported commands Savvio inquiry data Inquiry dataBytes Data hex Mode Sense data Mode Pages Mode Sense data for 900GB drivesMode Sense data for 600GB drives Mode Sense values for 450GB drives Mode Sense values for 300GB drives Miscellaneous status Miscellaneous operating features and conditionsMiscellaneous features Supported Feature or conditionSAS 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 IndexPage Msid Mtbf See also cooling Page Savvio 10K.5 SAS Product Manual, Rev. D Page Seagate Technology LLC

ST9600005SS, ST9600205SS, ST9300505SS, ST9300605SS, ST9300405SS specifications

Seagate has long been a prominent player in the storage solutions market, offering a range of hard drives that cater to various needs and applications. Among its extensive lineup, the Seagate ST9600105SS, ST9450405SS, ST9450305SS, ST9900605SS, and ST9900805SS stand out due to their unique features and robust performance, making them suitable for both personal and professional use.

The Seagate ST9600105SS is a 2.5-inch 600GB SAS hard drive that delivers exceptional reliability and performance. With a rotational speed of 10,000 RPM, this drive ensures quick data access through its enhanced data transfer rate. It utilizes a SAS 6Gb/s interface, allowing for fast and efficient data management in enterprise environments. The drive is designed with Seagate's AgileArray technology, which optimizes drive reliability for multi-drive environments, ensuring that users benefit from reduced downtime.

Similarly, the ST9450405SS and ST9450305SS are also 2.5-inch SAS drives, offering capacities of 450GB and 300GB, respectively. Both models feature a 10,000 RPM speed and a 6Gb/s SAS interface, making them ideal for use in data centers and business-critical applications. The ST9450405SS has enhanced power efficiency, aiding in lowering operational costs for enterprises. Both drives incorporate Seagate's advanced error recovery controls, which help maintain data integrity under varying workloads.

On the larger capacity side, the Seagate ST9900605SS and ST9900805SS drives provide even more storage options. Offering 600GB and 800GB capacities, respectively, these drives are designed for high-performance computing environments. They also spin at 10,000 RPM and support the 6Gb/s SAS interface. The ST9900805SS, in particular, is noted for its advanced performance in transactional workloads, making it suitable for database storage, virtualization, and analytics.

All five models feature Seagate’s innovative technologies, including firmware enhancements for improved error correction and reliability. They are also built to operate in a variety of environments, offering robust vibration tolerance.

In summary, the Seagate ST9600105SS, ST9450405SS, ST9450305SS, ST9900605SS, and ST9900805SS represent some of the best storage solutions for high-demand applications. With their emphasis on performance, reliability, and energy efficiency, these drives are engineered to meet the challenges of modern data storage needs, ensuring organizations can rely on them for their critical operations.
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