0B36400 Western Digital Ultrastar DC HC320 8TB 7.2K RPM SAS 12Gbps Hard Drive

Detailed Technical Specifications & Architecture

At the heart of the Western Digital 0B36400 Ultrastar DC HC320’s performance lie its meticulously engineered specifications. These are not just numbers on a datasheet; they are the quantified promises of stability and speed that IT architects and procurement specialists rely upon when designing resilient infrastructure.

Capacity & Form Factor

The 8TB capacity point offers a strategic balance between density and value. It provides substantial storage volume within a single 3.5-inch industry-standard form factor, enabling efficient scaling of petabytes within standard server chassis and storage enclosures. This capacity is ideal for consolidating workloads and reducing the physical footprint and complexity associated with managing a higher number of lower-capacity drives.

Physical Interface & Protocol

SAS 12Gbps: The Enterprise Backbone

The drive utilizes a dual-port SAS 12Gb/s (SAS3) interface. This is a critical differentiator. Dual-port SAS provides two independent data paths to the drive, a fundamental feature for high-availability setups and multipath I/O configurations. If one server path or controller fails, the second port ensures continuous data access, eliminating a single point of failure. The 12Gb/s per-port bandwidth ensures minimal data transfer bottlenecks, especially when multiple drives are arrayed together.

Performance Mechanics

Rotational Speed & Cache

With a spindle speed of 7,200 RPM, the HC320 is optimized for a blend of high sequential throughput and responsive random access. This speed, coupled with a large 256MB cache buffer, allows the drive to efficiently manage incoming read/write requests. The cache acts as a high-speed staging area, smoothing out data flow between the fast SAS interface and the physical magnetic media, thereby improving overall transactional performance.

Areal Density & Technology

The 8TB capacity is achieved through advanced HelioSeal technology and high areal density recording. HelioSeal hermetically seals the drive with helium instead of air, drastically reducing internal drag and friction on the platters and actuators. This results in several key benefits: lower operating temperature, reduced power consumption, and the ability to pack more platters into the same form factor for higher capacity—all while improving long-term reliability.

Enterprise Reliability, Workload, & Endurance Features

For data center drives, specifications extend far beyond speed and capacity. Mean Time Between Failures (MTBF), Annualized Failure Rate (AFR), and workload ratings are the true metrics of trust. The Ultrastar HC320 is engineered to excel in these areas, providing peace of mind for mission-critical deployments.

Workload Rating & MTBF

The drive is rated for 550TB/year workload limits. This is not a storage limit but a measure of the amount of data written to and read from the drive annually that it is designed to sustain reliably over its warranty period. This high workload rating qualifies it for heavy-use scenarios such as big data analytics, content delivery networks, and multi-user database applications. Coupled with a 2.5 million hour MTBF, this translates to an exceptionally low predicted annual failure rate, maximizing system uptime and reducing total cost of ownership (TCO) related to drive replacements.

Advanced Technology for Data Integrity

Rotary Acceleration Feed Forward (RAFF)

In multi-drive systems, vibration from neighboring disks can degrade performance and accuracy. The HC320 incorporates RAFF technology to actively monitor and compensate for both rotational and translational vibrations. This ensures consistent seek performance and data integrity even in fully populated, high-performance storage enclosures.

Error Correction & Protection

The drive employs sophisticated Triple-stage Actuator (TSA) technology and advanced error correction codes (ECC). The TSA system uses a dual-stage microactuator coupled with the main voice coil motor to enable extremely precise head positioning. This allows for tighter track spacing (higher density) and more accurate reading/writing, reducing errors and improving resilience against physical disturbances.

Primary Use Cases & Ideal Applications

The Western Digital 0B36400 Ultrastar HC320 8TB SAS drive is not a general-purpose drive; it is a specialist. Its combination of capacity, SAS performance, and robust endurance makes it the storage medium of choice for specific, demanding IT environments.

Data Center Server Storage

As a primary drive in enterprise servers for operating systems, hypervisors (like VMware vSphere, Microsoft Hyper-V), and applications, the HC320 delivers the necessary I/O consistency and low latency. Its dual-port SAS capability is essential for servers configured for failover clustering or connected to shared SAS storage shelves.

Storage Area Networks (SAN) & NAS Systems

In SAN arrays and scale-out NAS systems, multiple HC320 drives can be configured in RAID groups (RAID 5, 6, 10, etc.) to create large, fault-tolerant, and high-performance storage pools. The 12Gbps SAS interface ensures back-end drive connectivity does not become the bottleneck, allowing the storage controllers to fully utilize network bandwidth (10GbE, 25GbE, Fiber Channel) to serve data to connected hosts.

High-Performance Data Analytics & Archives

Big Data & Object Storage

For big data platforms like Hadoop or large-scale object storage deployments (supporting S3 or Swift APIs), the HC320 offers an excellent balance of cost-per-TB and throughput. Its high sustained sequential read/write speeds are ideal for processing large datasets and storing vast amounts of unstructured data, such as logs, sensor data, and media archives.

Media, Entertainment, & Surveillance

The drive's high capacity and sequential performance make it perfect for video editing and broadcast storage, where multiple high-bitrate 4K/8K streams must be read and written simultaneously. Similarly, in large-scale IP video surveillance systems (VMS), the HC320 can reliably handle continuous writes from hundreds of cameras, storing weeks or months of footage in a dense, reliable format.

Understanding the Category: SAS vs. SATA & RPM Considerations

Placing the 0B36400 Ultrastar HC320 in the broader storage landscape clarifies its targeted value proposition. The choice between SAS and SATA, and between different RPM tiers, is fundamental to system design.

SAS vs. SATA Enterprise Drives

While both may share similar capacities and form factors, SAS drives like the HC320 are built for fundamentally different duty cycles than enterprise SATA drives. Key advantages of SAS include:

Dual-Port Redundancy: Essential for mission-critical availability, a feature absent in SATA.
Higher Interface Speed: 12Gbps SAS vs. 6Gbps SATA, doubling the potential bandwidth per drive.
Full-Duplex Communication: SAS can read and write data simultaneously, unlike SATA's half-duplex.
Larger Command Queue: Supports deeper command queues (typically 256+ vs. 32 for SATA), drastically improving performance in heavy, random I/O scenarios common in database and virtualization workloads.
Enhanced Error Reporting: More detailed telemetry for proactive health monitoring in large systems.

7,200 RPM in the Enterprise Spectrum

Within the enterprise HDD segment, spindle speeds typically range from 5,400 RPM (often for nearline SATA storage) to 10,000 and 15,000 RPM (for ultra-high-performance SAS). The 7,200 RPM class, as embodied by the HC320, has become the mainstream sweet spot. It delivers 90-95% of the sequential performance of a 10K RPM drive for large file transfers while offering significantly higher capacities (8TB, 10TB, 12TB+, etc.) and better power efficiency per terabyte. For the vast majority of data center applications where capacity, throughput, and TCO are paramount, 7.2K RPM SAS drives provide the optimal balance.

Compatibility & Interoperability

The Ultrastar HC320 8TB SAS (0B36400) is designed for broad compatibility with industry-standard 3.5-inch hot-swap drive bays found in servers and storage systems from major OEMs like Dell EMC, HPE, Lenovo, Cisco, and Supermicro, as well as with enterprise-grade SAS HBAs and RAID controllers from Broadcom (formerly Avago), Microchip (formerly Microsemi), and others. Its SAS 12Gbps interface is backward compatible with earlier 6Gbps and 3Gbps SAS infrastructures, ensuring seamless integration into legacy environments, though performance will align with the slower link speed.