How much storage fits in the TerraMaster F4-425?
By Devin Chua · Data checked by Owen Nakamura · Updated · Prices checked The TerraMaster F4-425 takes 4 drives, up to 120 TB raw, but usable is the number that matters: 4 × 8 TB in TRAID gives 21.83 TiB for about CA$2,288 in drives, and it survives 1 drive failing. The gap from raw capacity is parity, and TRAID lets you grow with mixed drive sizes.
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Want to know whether the F4-425 fits your actual storage plan? Open the NAS Builder with this model weighted.
Usable space in the F4-425, by drive size
All 4 bays filled with equal drives in TRAID, the F4-425’s sensible default. Usable TiB is what the NAS reports; TB is the drive maker’s unit.
| Drive size | Raw | Usable (TB) | Usable (TiB) | Drive failures survived |
|---|---|---|---|---|
| 4 × 4 TB | 16 TB | 12 TB | 10.91 TiB | 1 |
| 4 × 8 TB | 32 TB | 24 TB | 21.83 TiB | 1 |
| 4 × 12 TB | 48 TB | 36 TB | 32.74 TiB | 1 |
| 4 × 16 TB | 64 TB | 48 TB | 43.66 TiB | 1 |
| 4 × 20 TB | 80 TB | 60 TB | 54.57 TiB | 1 |
| 4 × 24 TB | 96 TB | 72 TB | 65.48 TiB | 1 |
How much space you actually need
Start from what you store today, not from the drive sizes. As rough guides: a 24-megapixel RAW photo is about 25 to 30 MB, a phone photo 3 to 5 MB, and an hour of 4K phone video around 20 GB; check a folder of your own files for real numbers. Add the growth you expect over the next three to five years, then keep about 20 percent free so the pool does not run full.
Then plan the backup copy. RAID keeps the F4-425 running through a drive failure; it does not protect against deletion, ransomware, theft or fire. Size a second copy (an external drive, a second NAS or a cloud plan) for the data you cannot replace, which is often far less than the array.
For your own mix of drive sizes and RAID types, use the F4-425 capacity calculator. For drives that fit and their current Amazon.ca prices, see the best drives for the F4-425.
A worked configuration for the F4-425
WD Red Pro or Seagate IronWolf Pro in every bay is the recommendation for the F4-425. At 4 × 8 TB in TRAID, the F4-425 lands 21.83 TiB usable for about CA$2,288 in drives, gives up 8 TB to parity, and survives 1 drive failing. Step the same 4 bays of the F4-425 up to 16 TB drives and it holds roughly twice that, at the CA$/TB the live table above shows.
TRAID or RAID 6 in the F4-425?
With 4 bays the F4-425 gives a real choice. In TRAID it keeps 21.83 TiB of the 4 × 8 TB and survives one failure; RAID 6 spends one more drive for two. The trade tips with large drives: after a failure the F4-425 must read every surviving drive in full to rebuild, which on 20 TB drives runs the better part of a day under peak load. So from 16 TB per drive up, RAID 6 is the calmer choice in the F4-425.
One rule holds on every NAS, the F4-425 included: use CMR drives, not SMR. SMR drives rewrite overlapping tracks and collapse during a RAID rebuild, dragging a repair from hours into days.
Drive policy: TerraMaster locks no drive brand on the F4-425; its compatibility list is guidance, not a gate. The F4-425’s full compatibility rules.
Keep calculating
To see how much capacity is left after parity, the F4-425 capacity calculator is preset to its 4 bays and RAID types. For the F4-425, the wider basics of choosing a drive are in the buying guides, and CMR versus SMR explains why SMR drives do not belong in a RAID array. Wondering what the F4-425 can actually do: Plex, Immich, Docker, VMs? See what the F4-425 can run.
Frequently asked questions
What is the maximum storage in the F4-425?
4 drives, up to 120 TB raw per the manufacturer. 4 × 30 TB, per the manufacturer
How much of the F4-425 is actually usable?
In the F4-425, 4 × 8 TB in TRAID yields about 21.83 TiB: that is 24 TB in drive-maker terms, with 8 TB to parity. It shows less than the label because it counts in powers of two.
Can I fit larger drives in the F4-425 later?
Yes, and with TRAID it is easy: swap the F4-425's drives for larger ones one at a time, and the gain arrives once the second-largest drive is also larger.
Can I put third-party drives in the F4-425?
Yes. TerraMaster locks no drive brand on the F4-425; its compatibility list is guidance, not a gate.
Devin Chua works out which drives, RAM and NVMe cache fit which NAS model at nasdrives.ca, and what the RAID choice means for usable capacity, checked against what is in stock on Amazon.ca.
Data checked by Owen Nakamura, Technical editor (data checking)