TerraMaster F4-421 (2021) NAS Review

  • Link aggregation over two 1GbE ports
  • Good performance for its price
  • HDMI for console log monitoring
  • Decent selection of apps including Docker and Nextcloud
  • RAM expandable up to 8GB
  • Very loud fans
  • Drives have to be screwed in slots

The world today revolves around digital data and its processing, from the content we view on the Web to the new breeds of cryptocurrencies disrupting the financial status quo. While local data storage has become important even in the age of the cloud, data backups have become even more critical because of our dependence on our files for entertainment and work. As Network Attached Storage or NAS products have popped up left and right to cater even to home or small office users, we've test the new TerraMaster F4-421 2021 Edition to see if it fits the bill for a reliable on-site repository of your digital life.


Truth be told, the design of NAS boxes hasn't exactly changed that much over the years, and each brand tends to stick to what they've been sporting over different generations. The only immediate ways you'll be able to distinguish one model from another is often the number of drive bays they have on the front as well as the slots they offer on the back. In that vein, the TerraMaster F4-421 does have an uncanny resemblance to the F5-422 we reviewed earlier this year, except that this one has only four drive bays instead of five.

Those drive bays do come out easily enough as you would expect, simply by lifting the cover for each bay and sliding out the sleds. Attaching and removing drives, however, are completely different stories, as you will need a screwdriver to mount or detach the drives in place. Each sled accommodates 3.5-inch and 2.5-inch SATA HDDs or 2.5-inch SATA SDDs, for a total maximum capacity of 72TB, depending on the RAID configuration.

The back is arguably the more interesting part of the NAS box, and it is also where things get a bit confusing if you've been following TerraMaster's products closely. The company actually launched an F4-421 NAS back in 2019, and this is a silent and very different refresh of the same model. The ports and arrangement of ports are significantly different on this new model, resulting in a product that has a significantly different set of abilities.

Specs and performance

The TerraMaster F4-421 (2021) seems to be a downgrade from its predecessor if we look at the number of Ethernet ports alone – what was four is now only two. But with that change comes space for an upgrade. It is finally possible to use link aggregation to use those two 1GbE ports together, a feature that's almost a standard on NAS these days. Just like before, however, there is no 10GbE port.

Inside the box is a quad-core Intel Celeron J3455 running at 1.5GHz with a max burst of up to 2.3GHz. There is 4GB of RAM soldered on board, but there's also an expansion slot for adding up to 4GB more. All-in-all, the TerraMaster F4-421 (2021) has enough muscle to handle almost all data processing needs, from transcoding media to AES encryption to backups to, of course, RAID.

The NAS supports multiple RAID types, including Single, JBOD, RAID 0, RAID 1, RAID5, RAID 6, and RAID 10. For our tests, we used to maximize data protection while also pushing the hardware to its limits. Our experience is quite positive, with performance that's almost on par with more expensive products like the DiskStation Synology DS920+. Copying a large 12GB 4K video over the single 1GbE averaged at around 37 MB/s, while HD video playback from the NAS was a smooth 110 MB/s.

One of the very few criticisms we have for the TerraMaster F4-421 is the very audible noise from the dual 80mm fans that should only be as loud as 19.8dB(A). The fan actually has three settings, but even the lowest one was loud to our ears.

A unique feature of the TerraMaster F4-421, both old and new, is the HDMI port. No, it can't be used as a traditional display to access the graphical user interface (more on that later) or watch videos stored on the drives. It is, instead, more of a diagnostic tool that dumps you into a console debugger, which can be handy when you can't access the box through the network because of an error or problem.


Like any other TerraMaster NAS, the F4-421 (2021) runs the company's Linux-based TOS, short for TerraMaster OS. It presents an easy-to-use graphical environment that's like a mix of Windows and the old Mac OS X. The OS comes with a few utilities out of the box for managing files, users, disks, and RAID configurations, but like any other NAS OS, its true power comes from the apps.

TOS doesn't have as many apps on its catalog, at least not compared to the likes of Synology's DiskStation Manager (DSM) or ASUSTOR Disk Manager (ADM). It does, however, have the essentials, like media servers (Plex), torrent clients (Transmission), backup sync to Dropbox or Google Drive, and the like. The selection might seem a bit drab, but two apps do make up for almost everything else that the collection lacks.

Nextcloud and its extensions, for example, can replicate much of the missing functionality you might have become familiar with from Synology. Docker, on the other hand, opens the door wide to installing software images, including other Linux distributions, that will let you customize your experience as you wish. Of course, these require more advanced familiarity, but the average user won't be straying far from what TOS offers anyway.


The data storage and backup needs of homes and especially small businesses have become more complicated over the past years, but budgets haven't always scaled up proportionally. The need for an affordable but reliable storage solution has never been more important, and the TerraMaster F4-421 (2021 model) checks most of the boxes, at least the most essential ones.

Yes, the fan noise was annoying, and some might find the few dozen apps a bit disappointing. But with a solid performance for a $470 NAS, along with the newly added link aggregation and RAM expansion, the TerraMaster F4-421 (2021) is definitely something you might want to consider putting on your list during this shopping spree season.