Western Digital WUH722020CL5204 Ultrastar DC Hc555 20TB 7.2K RPM SAS 12GBPS HDD.

Western Digital WUH722020CL5204 Ultrastar DC HC555 Enterprise HDD Overview

This enterprise-class hard disk drive is engineered for data centers requiring immense storage and unwavering reliability. The model represents a pinnacle of high-capacity data storage technology.

Primary Specifications and Product Identification

Manufactured by the industry leader, Western Digital, this unit is a cornerstone of their enterprise storage solutions. It is a vital component for building robust and scalable storage infrastructures.

Product Line and Series Details

• Manufacturer Brand: Western Digital
• Model Identifier: WUH722020CL5204
• Device Classification: Internal Hard Disk Drive
• Product Family: Ultrastar
• Series Designation: Ultrastar DC HC555
• Full Product Title: Ultrastar DC HC555 20TB Enterprise Hard Drive

Optimal Deployment Scenarios

This storage solution is architected for the most demanding computational environments where data integrity and volume are paramount.

Target Applications and Use Cases

• Hyperscale computing and massive data repositories
• Deep learning and artificial intelligence data lakes
• Integrated and converged infrastructure systems
• Public, private, and hybrid cloud storage platforms

Defining Characteristics and Attributes

The device incorporates advanced technologies to deliver exceptional performance and resilience for 24/7 operation.

Core Technical Features

• Total Data Space: 20 Terabytes
• Form Factor: 3.5-inch internal enclosure
• Host Bus Interface: SAS 12Gb/s
• Reliability Metric (MTBF): 2.5 million hours

Performance Metrics and Operational Speed

Engineered for high-throughput applications, this HDD ensures rapid data access and transfer, minimizing latency.

Speed and Data Handling Capabilities

• Maximum External Transfer Rate: 1200 MB/s
• Sustained Data Throughput: 285 MB/s
• Average Delay Time: 4.16 ms
• Integrated Cache Memory: 512 MB
• Spindle Rotation Velocity: 7200 RPM

Physical Dimensions and Build

The drive is constructed with a compact footprint, allowing for efficient utilization of rack space within storage servers.

Form Factor and Mass Specifications

• Height (Z-axis): 26.1 mm
• Width and Depth Measurements: 101.6 mm x 147 mm
• Unit Mass: 690 grams

Advanced Internal Technology

Utilizing helium-sealing technology, this drive reduces aerodynamic drag inside the enclosure, resulting in lower power consumption and enhanced operational efficiency.

Western Digital WUH722020CL5204 Ultrastar DC HC555 — Enterprise 20TB SAS Helium HDD Overview

The Western Digital WUH722020CL5204 Ultrastar DC HC555 20TB is a high-capacity, enterprise-class hard disk drive engineered for modern data center workloads. Built on a helium-sealed 3.5-inch platform and designed for 12 Gb/s SAS connectivity, this drive blends high storage density with enterprise-grade reliability, making it an ideal fit for nearline storage, object storage, cold/active archive and hyperscale cloud environments. Its 7,200 RPM spindle speed, large 512 MB cache, and 512e sector emulation deliver a balance of sequential throughput and efficient random access for mixed workload scenarios.

Key selling points

• 20 TB raw capacity in a 3.5-inch form factor — high density for rack-space efficiency.
• 12 Gb/s SAS interface for robust, enterprise-ready connectivity and multi-pathing.
• Helium-sealed platform reduces internal turbulence and power consumption compared with air-filled designs.
• 7200 RPM spindle speed with 512 MB DRAM cache — tuned for throughput and queue depth under heavy loads.
• 512e sector emulation for compatibility with legacy host systems while enabling higher areal density.
• Optimized for cloud-scale and hyperscale storage architectures — excellent for HDD-dominant tiers.

Performance characteristics

Performance for enterprise nearline HDDs is measured differently than for NVMe or high-performance SAS SSDs. The Ultrastar DC HC555 prioritizes sustained sequential throughput, predictable service times, and power-efficiency at scale. Typical performance traits include:

Sequential throughput

With a 7200 RPM spindle and a modern helium media stack, sequential read/write throughput is tuned for streaming workloads—large-object writes, tape-replacement archives, backup / restore tasks, and media streaming where high MB/s per drive is valuable. Deployments that require sustained multi-gigabyte-per-second transfers across dense HDD arrays benefit directly from this design.

Random I/O and latency

While random IOPS are lower than those delivered by SSDs, the Ultrastar DC HC555 is engineered to provide consistent randomized read latency suitable for metadata-heavy object stores and distributed file systems. The 512 MB cache and SAS 12 Gb/s interface mitigate some of the latency impact by smoothing bursts and improving multi-command handling.

Concurrency and queue depth

Enterprise applications with high queue depths—such as erasure-coding rebuilds, rebalancing tasks, or parallel backup jobs—will benefit from the drive’s ability to sustain throughput under heavy queuing. Systems leveraging SAS multipath I/O and intelligent host controllers can extract optimal performance when the drives are deployed in well-architected arrays.

Reliability, durability and enterprise features

Reliability is central to any enterprise HDD selection. The Ultrastar DC family emphasizes rugged design, extended MTBF/AFR characteristics, and firmware tuned for data-center operational patterns. Key reliability-focused elements include:

Helium-sealed technology

The hermetically sealed helium environment reduces aerodynamic drag and disk platter turbulence, resulting in lower power consumption, reduced heat generation, and improved long-term mechanical stability. Helium design is a major factor enabling the higher platter counts needed for 20 TB capacity in a 3.5" form factor.

Advanced vibration tolerance

Drives intended for dense enclosure deployment feature improved handling of rotational vibration (RV) and acoustics. This ensures sustained performance in large multi-drive shelves where neighbors can cause interference. Firmware-level RV compensation and mechanical dampening allow predictable operation in rack-dense servers.

Power-loss protection and data integrity

Enterprise-class firmware provides protection for in-flight data on power interruptions, coupled with error detection and correction mechanisms to help preserve data integrity. The combination of robust servo control, read/write channel design, and firmware error management reduces the chance of unrecoverable errors during normal and unexpected conditions.

Typical enterprise reliability metrics

• Designed for multi-year duty cycles and continuous operation in data center environments.
• High tolerance to environmental stressors (temperature, humidity, vibration) within enterprise spec ranges.
• Firmware optimized for background operations such as media scan, remapping, and SMART telemetry.

Compatibility and integration

Integration of Ultrastar-class drives into enterprise arrays, JBODs, or storage servers is straightforward when following best practices. The WUH722020CL5204 supports the SAS 12 Gb/s protocol, backward-compatible with 6 Gb/s and 3 Gb/s link speeds where necessary, and interoperates with a wide range of controllers, RAID cards, and HBA architectures.

Form factor and mechanical fit

The 3.5-inch form factor follows industry-standard dimensions for enterprise racks and enclosures. Ensure your enclosure supports helium-sealed models (most vendors do), and verify that drive bays, sleds, and backplanes provide reliable power and SAS signal integrity for 12 Gb/s operation.

Firmware and host interoperability

Enterprise deployments benefit when drive firmware versions are validated against the host OS and storage controller firmware. Vendors typically publish tested compatibility matrices; align drive firmware levels with your storage vendor’s recommended versions to minimize surprises around SMART parameter interpretation and advanced features.

Hot-swap and serviceability

The Ultrastar DC HC555 is intended for hot-swap capable systems. Drives should be installed in carriers or sleds that support tool-less removal and provide mechanical latching, allowing technicians to replace failed drives quickly while maintaining system uptime.

Use cases and deployment scenarios

The Ultrastar DC HC555 is tailored for capacity-optimized tiers in enterprise storage stacks. Common use cases include:

Cloud object storage

Object-store platforms (such as Ceph, Amazon S3-compatible systems, and proprietary object stores) benefit from high-capacity HDDs in their storage nodes. The 20 TB drives reduce node count per capacity target and improve rack-level density economics.

Nearline and cold storage

For data that is accessed infrequently but still needs relatively fast restores—such as compliance archives, backups, and cold tier content—the Ultrastar DC HC555 offers an economical balance of capacity and access performance.

Backup targets and secondary storage

Backup appliances, deduplication nodes, and disk-targeted backup libraries use large-capacity HDDs to hold many restore points. The drive’s sustained throughput improves backup and restore windows compared to lower-capacity alternatives.

Big data and analytics (capacity tier)

Analytical platforms often keep historical datasets online for long-term trend analysis. The Ultrastar DC HC555 allows organizations to retain more data on spinning media, reducing the expense of storing older data on flash-based tiers.

Power, thermal and acoustic considerations

While helium drives consume less power per terabyte than many air-filled equivalents, overall system power and cooling considerations must still account for large arrays of drives. Proper airflow management, power provisioning, and acoustic planning ensure healthy, efficient operation.

Power consumption

Expect improved watts-per-terabyte compared to earlier generations, but always validate idle and active power numbers on your vendor’s datasheet and consider workload characteristics (seek-heavy workloads increase power draw). For capacity planning, compute aggregate power per rack including drive count, controllers, and cooling overhead.

Thermal management

High-density shelves require disciplined airflow paths and validated fan curves in order to maintain safe operating temperatures. Helium drives radiate heat differently than air drives; follow the enclosure vendor’s guidance to maintain temperature within specified ranges.

Acoustics

Helium-sealed drives generally run quieter than comparable air-filled designs, but enclosure fan noise typically dominates in data centers. For on-prem deployments with noise-sensitive environments, compare measured dB(A) values and consult vendor performance notes.