Seagate ST3300007LW/LC, ST3146707LW/LC, ST373207LW/LC manual Prefetch operation

Page 25

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 generated.

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.

Tables 7, 8, and 9 show Mode default settings for the drives.

4.5.2Prefetch operation

If the Prefetch feature is enabled, data in contiguous logical blocks on the disc immediately beyond that which was requested by a Read command can be retrieved and stored in the buffer for immediate transfer from the buffer 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. Prefetch is enabled using 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 segment(s), the host can limit the amount of prefetch data to optimize system per- formance. 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 the Discontinuity (DISC) bit is set to one in bit 4 of byte 2 of Mode parameters page 08h.

Whenever 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 (unless changed by using a Mode Select command). For additional information about the PM bit, refer to the Unit Attention Parameters page (00h) of the Mode Sense command (1Ah) in the SCSI Interface Product Manual, part number 75789509.

Cheetah 10K.7 SCSI Product Manual, Rev. D

15

Image 25
Contents Cheetah 10K.7 Scsi Page Cheetah 10K.7 Scsi Page Revision status summary sheet Page Contents Installation Defect and error managementSeagate Technology support services Interface requirementsList of Figures Viii Cheetah 10K.7 Scsi Product Manual, Rev. D Cheetah 10K.7 Scsi family drive ST3300007LC shown ScopeCheetah 10K.7 Scsi Product Manual, Rev. D Standards Applicable standards and reference documentationElectromagnetic compatibility Electromagnetic susceptibilityEuropean Union Restriction of Hazardous Substances RoHS Electromagnetic complianceReference documents Cheetah 10K.7 Scsi Product Manual, Rev. D General description Media characteristics Standard featuresReliability PerformanceFormatted capacities Options factory installed Factory installed accessoriesAccessories user installed Programmable drive capacityInternal drive characteristics transparent to user Performance characteristicsScsi performance characteristics visible to user Format command execution time minutes Access timeGeneralized performance characteristics Ultra320 ScsiPrefetch/multi-segmented cache control Start/stop timeCache operation Caching write data Prefetch operation Cheetah 10K.7 Scsi Product Manual, Rev. D Error rates Reliability specificationsRecoverable Errors Unrecoverable ErrorsSeek errors Reliability and servicePreventive maintenance Annualized Failure Rate AFRControlling S.M.A.R.T 4 S.M.A.R.TReporting control Performance impactDetermining rate Predictive failuresDrive Self Test DST Parameter Code DescriptionDST Failure Definition State of the drive prior to testingImplementation Invoking DSTShort test Function Code 001b Product warrantyExtended test Function Code 010b Log page entriesProduct repair and return information ShippingAC power requirements Physical/electrical specificationsDC power requirements ST3146707 SE mode LVD mode Conducted noise immunity Power sequencing3 12 V Current profile Typical ST3300007 drive +12 V current profile Typical ST3146707 drive +12 V current profile Typical ST373207 drive +12 V current profile ST3300007 Power dissipationST3146707 ST373207 Environmental limits TemperatureRelative humidity Effective altitude sea levelShock Shock and vibrationRecommended mounting Vibration Air cleanlinessCorrosive environment Acoustics Mechanical specificationsLW mounting configuration dimensions LC mounting configuration dimensions Drive error recovery procedures Defect and error managementDrive internal defects Page Scsi systems errors Media Pre-Scan Background Media ScanConfigure drive options InstallationDrive ID/option select header FormattingJ6 jumper header J5 jumper header on LW models only J2 option select header on LW models only RES Function descriptionCooling Drive orientationGrounding Drive mountingCheetah 10K.7 Scsi Product Manual, Rev. D General description Interface requirementsScsi interface messages supported Scsi interface commands supported Page Page Page Inquiry Vital Product data Mode Sense data Mode Sense 10 Byte Header Data 00 ae 00 10 00 00 00 08 11 17 73 30 00 00 02 00 ae 00 10 00 00 00 08 08 8b b9 98 00 00 02 Condition/feature supported by Scsi bus conditions and miscellaneous features supportedPhysical interface Synchronous data transferSynchronous data transfer periods supported 2 REQ/ACK offsetDC cable and connector PCB Scsi interface physical description Scsi interface cable requirements Mating connectorsCable requirements LC ModelsMating connectors for LC model drives Mating connectors for LW model drivesRight-angle to Pcba connectors Scsi daisy chain interface cabling for LW drives Nonshielded 68-pin Scsi device connector used on LW drives Nonshielded 80-pin Scsi SCA-2 connector, used on LC drives GND +DBP1 Charge Active LED OUT 4 REQ +REQ Active LED OUT 4 Electrical description LVD output characteristicsMultimode-SE and LVD alternatives General cable characteristics LVD input characteristicsSingle-ended drivers/receivers Cables for low voltage differential drivers/receivers LW drives Terminator requirements Terminator powerLC drives Disc drive Scsi timing Disc drive Scsi timing Drive activity LED Spindle status Command status LED statusInternet MySeagate Reseller.seagate.com Seagate Technology support servicesPresales Support Technical SupportData Recovery Services Authorized Service Centers Warranty ServiceData Recovery Services Call center Presales and Technical Support Warranty Service FAX services-All Europe toll callToll-free support numbers Asia/Pacific support services Publication feedback survey Cheetah 10K.7 Scsi Product Manual, Rev. D Numerics SymbolsPage Page PCB Page Cheetah 10K.7 Scsi Product Manual, Rev. D

ST3300007LW/LC, ST373207LW/LC, ST3146707LW/LC specifications

Seagate's ST3146707LW/LC, ST373207LW/LC, and ST3300007LW/LC are part of the company's renowned line of hard disk drives (HDDs), specifically designed for enterprise and high-performance computing environments. With their reliability and performance, these drives have become popular choices for data centers and critical applications requiring extensive storage capabilities.

One of the standout features of these models is their capacity to handle large volumes of data. The ST3146707LW/LC has a capacity of 146GB, while the ST373207LW/LC offers 73GB, and the ST3300007LW/LC comes with a substantial 300GB. These capacities make them well-suited for applications that require not only high storage space but also rapid access to data.

In terms of performance, these drives utilize a 10,000 RPM spindle speed, which significantly enhances data access times and overall performance. The combination of fast rotational speeds with Seagate's advanced caching algorithms allows for swift data retrieval, making these drives ideal for environments where speed is crucial.

These HDDs also employ the SCSI (Small Computer System Interface) interface, which promises high data transfer rates and reliability in enterprise-level applications. The Ultra320 SCSI interface can support transfer rates up to 320 MB/s, ensuring that the drives can efficiently communicate with other system components.

Another key technology featured in these models is Seagate's Adaptive Error Correction technology, which enhances data integrity and reliability. This feature helps in the detection and correction of errors that can occur during data transfer, reducing the risk of data loss.

Performance consistency is critical in enterprise environments, and these drives are built to endure the demands of 24/7 operation. They are designed with robust mechanisms to withstand temperature fluctuations, shock, and vibrations commonly found in data center settings.

In summary, the Seagate ST3146707LW/LC, ST373207LW/LC, and ST3300007LW/LC hard drives exemplify advanced features and technologies tailored for enterprise storage solutions. With significant capacities, impressive spindle speeds, SCSI connectivity, and reliability-focused technologies, these drives remain a valuable asset for businesses relying on stable and high-performance data storage.