Western Digital WDE2170, WDE4360 manual Command Queuing and Reordering, Media Defect Management

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Advanced Product Features

WD Enterprise WDE2170/WDE4360

3.8.Command Queuing and Reordering

The drives support both tagged and untagged queuing. Tagged queuing allows the drive to receive multiple I/O processes from each initiator. Untagged queuing allows the drive to receive a maximum of one I/O process from each initiator.

In order to use tagged command queuing, the initiator must set the disconnect privilege bit. This allows the drive to disconnect from the SCSI bus. It also allows the same or other initiators to connect to the drive and send additional commands. The drive returns a status of BUSY if the disconnect privilege bit is off and the drive has I/O processes in the command queue. The drive has the capability to queue up to 64 I/O processes. Upon receipt of the 65th I/O process, the drive returns a status of QUEUE FULL.

The drive can reorder I/O processes in the command queue. The order in which the drive executes I/O processes may differ from the order in which they were received.

Command reordering employs an algorithm which improves the throughput of the drive by attempting to minimize both the seek time and the rotational latency.

The drive uses a command aging feature to prevent the command reordering algorithm from keeping I/O processes waiting in the command queue for extended periods of time. The drive allows I/O processes to wait in the command queue for only a specified length of time before they are scheduled in the next I/O process.

3.9.Media Defect Management

Western Digital drives support a defect management algorithm that uses sector slipping. Defective sites are pushed down during a reassignment operation to maintain a sequential order. Spare sectors are placed throughout the drive to support this algorithm. This routine can be invoked by the drive when Auto-Read Reallocation/Auto-Write Reallocation (ARRE/AWRE) is enabled in MODE SELECT Page 1. If these functions are disabled, the drive reports status and may recommend that the host request a reassign.

3.10. Microcode Download

Western Digital drives support downloadable microcode via the SCSI WRITE BUFFER command. The supported modes include Download Microcode and Save, as well as Download Microcode with Offsets and Save. Download Microcode with Offsets is used when the buffer is limited to the full download and requires smaller partial downloads to complete the download task.

3.11. Reed Solomon ECC On-the-Fly

Error Correction Code (ECC) on-the-fly is a correction technique that reduces the uncorrectable read error rate in hardware. This provides a high degree of data integrity with no impact on the drive’s performance.

3.12. CRC Data Protection

Cyclic Redundancy Check (CRC) data protection is a feature that enhances data integrity. During a write operation, before a user data block enters the cache (data buffer), the SCSI controller generates CRC data (2 bytes) and attaches it to the user data block (usually 512 bytes). During a read operation, the SCSI controller reads each user data block and its CRC data in the cache, then verifies the CRC data as it transfers each user data block to the SCSI bus.

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RELEASED 04-08-97

4079-001045 Rev. B

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Contents Technical Reference Manual Western Digital 4079-001045 Rev. B Released Escription and F Eatures Installation and Maintenance List of Figures List of Tables Description and Features General DescriptionAdvanced Features Product FeaturesOptions Data Buffer of 1 MegabytePerformance Specifications SpecificationsPhysical Specifications Physical Specifications WDE2170WDE4360 Physical Dimensions Physical Metric Characteristic Dimension ToleranceMechanical Specifications Dimension Inches Millimeters067 069 Mounting Drive Axis Definition ReleasedWDE2170 Current Requirements and Power Dissipation Current Profile WDE2170 +12V Current ProfileBring-Up Sequence Input Voltage RequirementsRipple +12 VDC +5 VDCEnvironmental Specifications Shock and Vibration ShockVibration Operating Vibration Cooling Temperature and HumidityTemperature and Humidity Component Location MaximumAcoustics Mode Typical MaximumAtmospheric Pressure AltitudeDrive Baseplate Thermocouple Location Pcba Thermocouple Locations 4079-001045 Rev. B Released Reliability Specifications Agency Approvals Product SafetyElectromagnetic Compatibility EMC Embedded Servo Control Compatibility TestingSCSI-3 SPI Compliant Read Caching and Pre-FetchMicrocode Download Command Queuing and ReorderingMedia Defect Management Reed Solomon ECC On-the-FlyZoned Recording Headerless FormatLED Support Option Block Functions Error Recovery Operations Hot Plug/Unplug Support Scsi Interface and Command SET Physical Characteristics Pin DesignationOption Block OPTION/SIGNAL Pins Configuration Notes Option Block Pin AssignmentsPins 7 Pins 5 Pins 3 Pins 1 Scsi ID Jumper TablePower Connectors and Cables Scsi ConnectorsScsi Physical Interface Pin Scsi Connector Drive OutlineSignal Name Pin Number Signal NameIV E O U T L in E SINGLE-ENDED Scsi Connector Differential Scsi Connector Pin SCA-2 Scsi Connector Pin Scsi Connector Pin NumbersSINGLE-ENDED Scsi Connector Installation and Maintenance Electrostatic Discharge ESD ProtectionMaintaining the Drive Technical Support Glossary Internal status Glossary WD Enterprise WDE2170/WDE4360 Appendix A. U Nderstanding the Model Number Interface MatrixIndex WD Enterprise WDE2170/WDE4360 Index H0300 4/97

WDE4360, WDE2170 specifications

Western Digital, a leader in data storage, has introduced innovative products like the WDE2170 and WDE4360 drives, which showcase their commitment to cutting-edge technology and reliability. These models are designed for various applications, from personal computing to larger enterprise solutions.

The WDE2170 is a 2TB hard drive positioned for consumers who require substantial storage for multimedia files, documents, and applications. Its interface features a SATA III connection, providing a robust data transfer rate that can reach up to 6Gbps. This speed ensures that users can access their files quickly and efficiently. Notably, the WDE2170 is equipped with a large cache size that enhances its performance during read and write operations. This makes it an excellent choice for gamers and content creators who need rapid access to their files.

On the other hand, the WDE4360 stands out as a 4TB offering, aimed at professionals and businesses requiring higher capacities. It utilizes advanced data management technologies to ensure data integrity and durability. With a focus on security features, the WDE4360 includes built-in encryption options to protect sensitive information. This model also utilizes advanced error recovery technology, which is vital for maintaining data integrity in RAID configurations or server setups.

Both models are built using Western Digital’s proprietary technologies that emphasize reliability and longevity. The drives are designed to withstand rigorous usage scenarios, making them perfect for environments where data access and protection are paramount. Additionally, these drives have low power consumption, which can help reduce operational costs, especially in larger installations.

The overall design of these drives is tailored for optimal performance and heat dissipation, ensuring that they can function effectively even under heavy loads. Western Digital's commitment to quality means that both the WDE2170 and WDE4360 undergo stringent testing processes to meet high standards of reliability before reaching the consumer market.

In conclusion, the Western Digital WDE2170 and WDE4360 are exceptional storage solutions, providing consumers and businesses with the speed, capacity, and reliability they need. These drives exemplify Western Digital's dedication to innovation and quality in the ever-evolving world of data storage. As data requirements continue to grow, these drives are sure to meet the demands of a diverse array of users.
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