TerraMaster U4-423 review: A worthy NAS for small businesses

The TerraMaster U4-423 is a budget rack NAS offering good 2.5GbE performance and plenty of data-protection services

The TerraMaster U4-423 on the ITPro background
(Image: © Future)

IT Pro Verdict


  • +

    Well built

  • +

    Good performance

  • +

    An abundance of data protection features


  • -

    Teething issues with some TOS 5 apps

Joining a burgeoning family of small business NAS appliances, the TerraMaster U4-423 offers an affordable storage solution that will slip easily into the smallest of spaces. 

Measuring only 360mm deep, this competitively priced 1U rack NAS presents four hot-swap LFF/SFF SATA drive bays and partners them with dual 2.5GbE multi-gigabit ports.

There's plenty of power on tap, with the appliance sporting a 2GHz quad-core Celeron N5095 CPU, while the base 4GB of DDR4 memory can be upgraded to a very usable 32GB. It also has an internal M.2 NVMe SSD slot, which can be used for caching or as a small high-performance storage pool.

Build quality is great. The U4-423 is clothed in a solid steel chassis and employs equally sturdy metal drive carriers. It's also an excellent choice for small office environments as the appliance's three 4cm diameter cooling fans are almost inaudible, even on their highest setting.

For performance testing, we installed four 10TB Seagate IronWolf NAS drives and used the web browser quick start wizard to install the latest TOS 5 software and create a 30TB TRAID array. All traditional RAID arrays are supported but TRAID can use drives of different sizes without any inherent loss in capacity.

The U4-423 delivers good performance, with a NAS share mapped to Windows Server 2019 host over a 2.5GbE link returning Iometer sequential read and write rates of 2.2Gbits/sec and 2.1Gbits/sec. It handled our real-world tests well, with drag-and-drop copies of a 25GB test file between the appliance and server averaging read and write rates of 2.3Gbits/sec and 2Gbits/sec, while a 22.4GB folder with 10,500 small files was secured at an average of 1.2Gbits/sec. 

Moving to IP SANs tests saw a 500GB iSCSI target deliver read and write rates of 2.2Gbits/sec and 2.1Gbits/sec. With a dual 2.5GbE MPIO link, these figures increased to 4.3Gbits/sec and 4.1Gbits/sec. Adding a 480GB Kingston NVMe SSD as a read/write cache saw 7% and 633% improvements to random read and write IOPS. 

TerraMaster U4-423 review: Security

TOS 5 has a sharp focus on data security, with the HyperLock-WORM feature stopping data on assigned Btrfs volumes from being deleted, modified or renamed for custom periods of up to 70 years and, once set, these cannot be reduced. The Security Advisor app advises on potential security issues, and at any time you can enable the System Isolation Mode, which blocks all internet, SSH and Telnet access and stops unsigned apps running. Data-protection services are plentiful, with the main Backup app providing a central location for managing all associated modules.

Rsync jobs replicate data to remote appliances, Btfrs file system snapshots can be run at regular intervals, the TerraMaster folder mirror creates local or remote copies of shared folders and CloudSync supports ten storage providers including Amazon S3, Box and Dropbox.

The TerraMaster U4-423 dashboard

(Image credit: Future)

Although still in beta testing, we confirmed that the Centralized Backup app now correctly performs Hyper-V VM backups and restores but noted that support for VMware is currently unavailable. The TerraSync Server app provides private cloud and file syncing services but is of limited value as the Windows sync client is still in development.

The Snapshot app supports NAS shares and thinly provisioned iSCSI LUNs and can run these as often as every hour. Restoration is easy: you choose a source, select a snapshot from the list presented and roll back to the desired point in time.

TerraMaster's affordable U4-423 is a worthy contender for small businesses as it puts big storage in small spaces. Performance over 2.5GbE is good and, although there's work still to be done on some TOS 5 apps, general data-protection apps are in abundance.

TerraMaster U4-423 specifications

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Chassis1U rack chassis
CPU2GHz quad-core Intel Celeron N5095
Memory4GB DDR4 (max 32GB)
Storage4 x LFF/SFF SATA hot-swap drive bays
RAIDSupports RAID0, 1, 5, 6, 10, TRAID
Warranty2yr limited warranty
Dave Mitchell

Dave is an IT consultant and freelance journalist specialising in hands-on reviews of computer networking products covering all market sectors from small businesses to enterprises. Founder of Binary Testing Ltd – the UK’s premier independent network testing laboratory - Dave has over 45 years of experience in the IT industry.

Dave has produced many thousands of in-depth business networking product reviews from his lab which have been reproduced globally. Writing for ITPro and its sister title, PC Pro, he covers all areas of business IT infrastructure, including servers, storage, network security, data protection, cloud, infrastructure and services.