TerraMaster F4-421 Review 4-Bay NAS for SMB Users

TerraMaster F4 421
TerraMaster F4 421

Recently, we looked at a trio of 2 bay NAS units from TerraMaster, the F2-220, F2-210 and F2-221. Today we have our first TerraMaster 4-Bay NAS to review, the F4-421. The TerraMaster F4-421 features a quad-core Intel Celeron J3455 processor. The F4-421 is designed for small-medium business and advanced users offering automatic scheduled backups, snapshots, multi-RAID array security. In our review, we are going to look at the TerraMaster F4-421 hardware and software. We are also going to run it through our benchmark suite to see how it performs.

TerraMaster F4-421 4-Bay NAS Overview

The TerraMaster F4-421 4-Bay NAS looks exactly like the 2-bay NAS units we have looked at before from the company. The main difference being the two extra drive bays. Additional options on the F4-421 include two extra RJ45 1GbE network ports and a HDMI port. We see the same TOS operating system and accessory loadout as in our previous reviews.

After removing the TerraMaster F4-421 from its packing material, one gets a clear look at the NAS.

TerraMaster F2 421 Front
TerraMaster F4 421 Front

The enclosure of the F4-421 looks identical to the 2-bay units that we have reviewed before, except for the two extra drive bays. Looking at the front, we find a silver power button on the left side with status LED’s above.

The back of the NAS has 2x USB 3.0 ports, 4x RJ-45 1GbE LAN Ports, a HDMI port and power connector.

TerraMaster F2 421 Back
TerraMaster F4 421 Back

One conspicuously absent feature is either 10GbE or even 2.5GbE/ 5GbE ports. In 2019, we are seeing NAS vendors utilize some of the lower-cost options for faster networking speeds and we would have liked to have seen TerraMaster include this on its 4-bay NAS.

Accessories included with the F4-421 include:

  • Quick Installation Guide
  • AC Power Adapter
  • AC Power Cord
  • RJ-45 LAN Cable
  • 2x package of assorted hard drive mounting screws
  • One small screwdriver

Two large 80mm cooling fan takes up the bulk of the space which provides the primary cooling for the NAS.

Installing Drives in the TerraMaster F4-421

Each TerraMaster F4-421 drive bay can accommodate either a 3.5″ or 2.5″ hard drive or solid state drive with capacities up to 14TB in size for a total of up to 56TB raw capacity. As larger drives are qualified, this capacity will rise. Users can add SSD caching to optimize read/ write operations. Doing so will consume a drive bay and therefore lower available hard drive capacity as the cache drives use the main hard drive bays.

TerraMaster F2 421 Drive Tray
TerraMaster F4 421 Drive Tray

The drive trays are not tool-less and will require mounting screws to secure the HDD to the drive tray. We think this is an area that the company can improve. After mounting they slide into the NAS and lock in place.

TerraMaster F2 421 Installing Hard Drives
TerraMaster F4 421 Installing Hard Drives

Let us take a look at the TOS NAS management software before moving on to testing the TerraMaster F4-421.


  1. Hi!
    It seems TerraMaster like to reuse the same backplane in several of their nas, and i saw a 4 bays model that had the backplane of the 5 bays model, hence you could dremel the front panel to use the fifth bay.
    Could you check if it is the case with this one? you could put a 2.5″ SSD inside the case to be used as a cache this way, without losing one of the 4 “official” bays… :)
    That would increase its value even more!


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