D4-320U
4-Bay Rack-Mounted Hard Drive Enclosure

Primary Applications of D4-320U

The D4-320U is a high-performance USB 3.2 direct-attachedstorage (DAS) device designed by TerraMaster for server storage expansion. It supports multiple operating systems, including Windows Server,various Linux distributions, Proxmox hosts, TrueNAS hosts, and Unraid hosts, providing users with a flexible and efficient storage expansion solution.
The D4-320U features a compact rack-mountable design, ideal for wall-mounted rack installations, saving space while ensuring stable operation. Its USB 3.2 Gen2 interface supports transfer speeds of up to 10Gbps, meeting the high-speed, large-capacity storage needs of small and medium-sized businesses. Whether for data backup, file sharing, or storage pool expansion, the D4-320U is an ideal choice.
Additionally, the D4-320U incorporates an intelligent temperature-controlled fan and silent operation design, ensuring efficiency and stability during prolonged use. Its plug-and-play functionality further simplifies installation and usage, making it suitable for users requiring rapid deployment of storage solutions.

Compact Design for Easy Installation

This 1U 4-bay direct-attached storage enclosure adopts a space-saving rack-mountable design. With a compact chassis depth of 241mm (9.49 inches) and a weight of 3.2kg, it requires no rails and is easy to install. The 1U height fits standard server racks, enabling centralized deployment with other servers and network equipment. This enhances data center space utilization and is suitable for server rooms, storage rooms, stairwells, offices, and other environments—perfect for small office users.

88TB Massive Storage Capacity

The D4-320U offers powerful storage expansion, supporting up to 4 drives. With a maximum single drive capacity of 22TB (compatibility with larger drives pending verification), it delivers up to 88TB of storage, meeting large-scale data storage needs. However,the device operates in single-disk mode by default; RAID configurations can be achieved using third-party software array management tools.

10Gbps High-Speed Data Transfer

Utilizing USB 3.2 Gen2 protocol, the D4-320U achieves data transfer speeds of up to 10Gbps. When equipped with four drives, actual read/write speeds can reach 1016MB/s (tested with 4x WD Red 8TB HDDs). With a single drive installed, read speeds still reach 510MB/s (tested with a WD Red 1TB SSD). Whether in multi-drive or single-drive configurations, the D4-320U delivers exceptional performance.

Driver-Free Plug-and-Play

True plug-and-play compatibility eliminates the need for drivers. It seamlessly supports cross-platform operating systems, including macOS, Windows, Linux, Ubuntu, TrueNAS, and Unraid. Fully compliant with USB protocols, it connects to PCs, TVs, servers, set-top boxes, and other devices, offering unparalleled convenience and flexibility.

Strong Compatibility

Interface Compatibility: Features a USB Type-C port and includes two 0.8-meter cables (USB-A to USB-C and USB-C to USB-C), ensuring seamless connectivity with USB 3.0, 3.1, 3.2, Thunderbolt 3, and Thunderbolt 4 ports for stable, high-efficiency data transfer.

Drive Compatibility: Supports 3.5-inch SATA HDDs, 2.5-inch SATA HDDs, and 2.5-inch SATA SSDs. For optimal stability and performance, consult TerraMaster’s drive compatibility list before purchasing.

Expanding NAS Storage

Professionally optimized by TerraMaster’s team, the D4-320U can connect to TerraMaster NAS devices via USB. Leveraging TerraMaster’s robust TOS system, users can create arrays and storage pools on the device to expand NAS storage capacity, addressing growing data demands. Note: This feature is only compatible with TerraMaster NAS devices running TOS 5.1 or later.

Multi-Layered Security Protection

Power Protection: Advanced power protection design activates immediately upon detecting incompatible power sources, preventing damage to the device and hard drives from overcurrent or voltage fluctuations.

Power-on Recovery Function: Equipped with power-on recovery memory. After normal shutdown, the device remains off upon power restoration. After abnormal power loss, it automatically restarts when power resumes, enabling automated unattended management with servers or NAS devices.

Intelligent Drive Sleep for Energy Efficiency

The D4-320U supports smart sleep mode, allowing drives to enter hibernation with the connected system. This reduces drive operating time, minimizes motor wear, and significantly extends drive lifespan—ensuring efficient storage while safeguarding your drive investments.

Quiet and Efficient Cooling

Equipped with a dual-ball bearing fan, the product delivers an exceptional 70,000-hour service life,combining robust reliability with uncompromising performance in harsh environments.
Its intelligent features ensure that the fan speed automatically adjusts based on the hard drive's temperature, maintaining the drive within an optimal operating temperature range.An optimized internal structure enhances airflow, reduces drive temperatures, minimizes component resonance, and maintains low noise levels even under full load—ideal for quiet work environments.

Automatic Backup

Using the user-friendly TPC Backupper tool for Windows, users can schedule backups. Connect the device to a PC, install the client, and configure tasks to back up folders or disk partitions to the TerraMaster USB device or NAS. Supports incremental and differential backup strategies for Windows 8/8.1/10/11 systems, delivering reliable protection for critical data. Download Now