2U short-depth design for up to 38% reduction in size
The rackmount TS-855eU has a short depth design of only 11.7 inches (297.4 mm), making it an excellent choice for smaller racks, wall-mount AV rack cabinets, and network rack cabinets. The space saved by the short depth design can be reserved for cabling or ventilation. The TS-855eU is space-saving for flexible deployment and is especially suitable for compact offices, audiovisual rooms, and security surveillance recording.
Note: Users can purchase the optional RAIL-S01 short rail kit to deploy the TS-855eU in a 19-inch rack following the ANSI/EIA-RS-310-D standard.
Ultimate 8-core performance with up to 64 GB RAM and Intel® QuickAssist Technology
Designed for heavy business workloads, the TS-855eU delivers exceptional 8-core performance for running multiple concurrent tasks. AES-NI encryption and Intel® QuickAssist Technology (QAT) is supported to offload computationally-intensive compression and improving IPsec/SSL cryptography performance. Up to 64 GB ECC RAM is supported. Combining high performance, reliability, and capacity, the TS-855eU is an all-round budget-friendly storage solution for diverse applications, such as file servers, high-speed storage/backup/recovery, and virtualization.

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Windows File Transfer (2 x 2.5GbE)
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Tested in QNAP Labs. Figures may vary by environment.
Test Environment:
NAS: TS-855eU with QXG-25G2SF-CX6
OS : QTS 5.0.1
Volume type: 8 x Samsung 860 EVO 1 TB SATA , RAID 5, thick volume
Client PC: Windows Server 2016 Standard, Intel i7-6700 3.4GHz, 64GB RAM
IOmeter: 16MB, 30-sec ramp up time, 3-min seq. run time, 16 workers, 4-outstanding
Affordable 2.5GbE meets high-bandwidth demands
With two 2.5GbE RJ45 LAN ports (backwards compatible with 1G/100M), the TS-855eU allows businesses to easily upgrade network speeds from 1 Gigabit to 2.5 Gigabit using existing CAT5e cables. Port Trunking and failover also reinforce applications demanding higher bandwidth and reliability, including virtualization, large file transfers, high-speed backup/restoration, and real-time applications. QNAP also offers numerous managed/unmanaged 2.5GbE/10GbE switches, assisting organizations in implementing high-speed, secure, and scalable network environments without going over budget.
Learn More: QNAP 2.5GbE solutions, QNAP Switch family

M.2 PCIe slots for SSD caching and accelerated AI-powered image recognition
The TS-855eU comes with two M.2 PCIe Gen 3 slots that allow for installing M.2 2280 NVMe SSDs or Edge TPU (sold separately) to boost NAS performance.
Abundant I/O capabilities with PCIe expansion
The TS-855eU has two PCIe Gen 3 x4 slots that allow for installing various expansion cards for expanding application potential.
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5/10/25GbE network card
Enable lightning-fast throughput for bandwidth-demanding tasks (virtualization, mass data transmission, and fast backup/restore).
Learn More: QNAP network expansion cards
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QM2 card
Add M.2 SSDs or 2.5GbE/10GbE connectivity to the TS-855eU for optimized performance and bandwidth.
Learn More: QM2 card
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SAS / SATA storage expansion cards
Connect the TS-855eU to SAS 12Gb/s or SATA 6Gb/s expansion units for petabyte-scale storage capacity.
Learn More: QNAP storage expansion cards, Compatible expansion enclosures
Build an affordable Fibre Channel SAN environment
Common Fibre Channel Storage Area Networks (SAN) devices are often costly. By installing QNAP dual-port 16Gb /32Gb Fibre Channel expansion cards in the TS-855eU, you have more budget-friendly options to add a NAS to a SAN environment. You can set a Fibre Channel Target using the iSCSI & Fibre Channel app. Moreover, the LUN Masking and Port Binding features provide an additional layer of data security.
Learn More: QNAP NAS supports Fibre Channel SAN, QNAP Fibre Channel cards

Simple Backup
Superior hardware performance with an all-in-one Backup Solution to speed up backup/recovery tasks.
Multi-version snapshots mitigate ransomware threats
The TS-855eU supports block-based snapshots that record the state of the system at any time. It helps protect data, which can be restored back to a specific point of time, greatly helping in mitigating the threat of ransomware.
Reliable, high-performance storage for virtualization
The TS-855eU supports block-based iSCSI LUN as a reliable, high-performance, and affordable storage solution for mainstream virtualization environments. It supports VMware® VAAI and Microsoft® ODX to increase performance by offloading server loading for ESXi server and Hyper-V respectively.


All-in-one solution for hosting virtual machines and containers
By running multiple virtual machines and containers on the TS-855eU, you can deploy multi-tenant environments and applications to increase management efficiency and save hardware costs. Coupled with the Network & Virtual Switch app that boosts interoperability between virtual machines, containers, QNAP NAS, and other physical devices on the network, you can flexibly allocate physical and virtual network resources to simplify network deployment.
Comprehensive security and privilege settings
The TS-855eU is loaded with flexible privilege settings and security measures. Besides IP blocking, QNAP Authenticator, HTTPS connection, there are more apps that help ensure optimal NAS protection against threats like malware and hackers.