WUH721818AL5200 Western Digital Ultrastar DC HC550 18TB 7.2K RPM SAS-12Gbps HDD

Overview of Western Digital WUH721818AL5200 18TB HDD

The Western Digital Ultrastar DC HC550 18TB enterprise hard drive is engineered for modern data-driven infrastructures that demand exceptional capacity, reliability, and consistent performance. Built on a helium-sealed platform, this internal 3.5-inch HDD is optimized for mission-critical workloads in large-scale storage ecosystems. As part of the trusted Ultrastar product line, it delivers enterprise-grade durability and efficiency for always-on environments.

General Information

• Brand: Western Digital
• Part Number: WUH721818AL5200
• Series: Ultrastar DC HC550
• Product Type: Hard Disk Drive

Technical Specifications

• Storage Capacity: 18TB
• Interface Type: SAS-12Gbps
• Sustained Data Transfer Rate: Up to 257 Mbps
• Rotational Speed: 7200 RPM
• Buffer Size: 512MB cache 

Drive Dimensions and Weight

• Form Factor: 3.5-inch internal hard drive
• Z-Height: 26.1 mm
• Dimensions (W x D): 101.6 mm x 147 mm
• Weight: Approximately 690 g

The Western Digital WUH721818AL5200 18TB 7.2K RPM HDD

The Western Digital WUH721818AL5200 Ultrastar DC HC550 18TB hard disk drive belongs to the enterprise HDD category engineered for data centers, cloud service providers, and large-scale storage infrastructures that demand exceptional capacity, reliability, and sustained performance. This category focuses on high-capacity 3.5-inch internal hard drives designed to handle mission-critical workloads where uptime, data integrity, and predictable latency are essential. With an impressive 18TB storage capacity, this drive addresses the continuous growth of unstructured data, analytics-driven environments, and large archival repositories.

Ultrastar DC HC550 HDD

The Ultrastar brand from Western Digital represents a long-standing legacy of enterprise storage innovation. Within this portfolio, the DC HC550 series occupies a critical position as a high-capacity, helium-sealed hard drive family optimized for data center workloads. This category is characterized by advanced mechanical engineering, enhanced firmware algorithms, and rigorous validation processes tailored for enterprise deployment.Drives in this category are purpose-built for 24x7 operation, delivering predictable performance and endurance in multi-drive enclosures. The WUH721818AL5200 model exemplifies this category by combining capacity efficiency with robust SAS connectivity, making it suitable for scale-out storage and dense rack environments.

18TB Storage HDD

The DC HC550 category addresses the growing demand for higher storage density without increasing physical footprint. By offering 18TB capacity in a standard 3.5-inch form factor, this subcategory allows organizations to maximize rack-level and data center-level storage efficiency. This approach reduces total cost of ownership by lowering power consumption per terabyte, minimizing cooling requirements, and optimizing floor space utilization.

Helium-Sealed Platform 

Helium Technology 

Helium-sealed hard disk drives represent a significant advancement within the enterprise storage category. The Ultrastar DC HC550 leverages a helium-filled enclosure that reduces internal turbulence, allowing for more platters and improved rotational stability. This category of helium HDDs delivers higher areal density while maintaining lower power draw and reduced operating temperatures.

Storage Class Design

This Ultrastar DC HC550 HDD is purpose-built for enterprise and data center deployments where storage density and operational efficiency are top priorities. The helium-filled design reduces internal turbulence, enabling higher platter counts, lower power consumption, and improved long-term reliability.

7.2K RPM Performance

The 7,200 RPM rotational speed defines a key performance tier within the enterprise HDD category. This speed strikes a balance between throughput, latency, and energy efficiency, making it ideal for bulk storage, nearline applications, and data-intensive workloads that require steady read/write performance.When paired with the SAS 12Gbps interface, drives in this category deliver high sustained transfer rates suitable for large sequential workloads, backups, media streaming, and analytics pipelines. The performance consistency of this category ensures predictable behavior under mixed workload conditions.

512MB Cache Buffer Advantages

The inclusion of a 512MB buffer places the WUH721818AL5200 in a premium enterprise HDD subcategory. This large cache helps optimize data flow, reduce access latency, and improve command queuing efficiency. In environments with multiple concurrent data streams, the cache plays a vital role in smoothing performance and minimizing bottlenecks.

SAS 12Gbps Interface

Serial Attached SCSI (SAS) is a defining characteristic of high-end enterprise HDD categories. The 12Gbps SAS interface used by the Ultrastar DC HC550 enables faster data transfer rates, robust error handling, and dual-port connectivity for redundancy. This makes the category suitable for mission-critical applications where continuous access to data is mandatory.

Dual-Port Architecture for High Availability

Dual-port SAS functionality allows the drive to connect to two independent controllers, ensuring uninterrupted data access in the event of a path failure. This feature is a cornerstone of enterprise storage categories, particularly in clustered storage systems and high-availability server architectures.

512e Advanced Format

The 512e (512-byte emulation) format represents a transitional storage format within enterprise HDD categories. While the physical sectors are 4K in size, the drive emulates 512-byte sectors for compatibility with existing operating systems and applications. This approach enables organizations to adopt higher-capacity drives without reengineering legacy software stacks.Drives in this category benefit from improved error correction and data integrity while maintaining broad compatibility across enterprise platforms.

Media & Entertainment Storage Solutions

The media and entertainment industry often handles massive files such as high‑resolution video, audio libraries, and CGI assets. The Ultrastar DC HC550 provides the combined capacity and sustained data throughput needed to archive and serve large media assets with confidence. Video editing suites, broadcast storage servers, and rendering farms all benefit from the high performance and reliability of this HDD series.

3.5‑inch Form Factor 

Featuring the standard 3.5‑inch form factor, the Ultrastar DC HC550 drives are compatible with most server chassis, storage arrays, and expansion enclosures. This ensures straightforward replacement or expansion planning when upgrading existing storage infrastructure. Compatible backplanes and hot‑swap bays allow for drive swaps with minimal downtime.