UniFi UNAS Pro 4: Specs, Drives and Total Build Cost
The UNAS Pro 4 is Ubiquiti's 4-bay network-attached storage appliance. Below is what Ubiquiti's own techspecs and store pages state about it, what it costs filled with drives today, and the honest state of its drive requirements.
Hardware specifications, per Ubiquiti's own pages
| Bays | 4 |
|---|---|
| Drive form factors | 4 x 2.5/3.5-inch HDD or SSD |
| M.2 slots | 2 x M.2 NVMe |
| M.2 purpose | SSD cache only, per Ubiquiti's own store page - max NVMe capacity 4TiB per Ubiquiti's techspecs page |
| Max single-drive capacity (main bays) | not published by Ubiquiti |
| RAM | 8GB shipped (Ubiquiti's own figure); type, ECC status and maximum not published |
| Network | 2 x 10G SFP+ (10G only) + 1 x GbE RJ45 (1G/100M/10M) |
| Expansion unit | not found on Ubiquiti's pages for this model |
| PSU | 150W (AC/DC, internal) |
| Published acoustic figure | not published by Ubiquiti |
Source: Ubiquiti UniFi UNAS Pro 4 technical specifications, read 2026-09-14 — techspecs.ui.com.
Ubiquiti's own store page labels these explicitly: "(2) M.2 NVMe SSD cache slots." Neither the store page nor the techspecs page mentions an independent M.2 storage-pool option for this model.
The honest total: chassis + drives, three ways
$699.00 buys the empty chassis. Filling all 4 bays is the real purchase, priced at three genuinely different tiers below.
Best value fill - UNAS Pro 4 + 4 drives
Usable capacity by RAID level: RAID 1 20TB ($102.00/usable TB) · RAID 5 60TB ($34.00/usable TB) · RAID 6 40TB ($51.00/usable TB) · RAID 10 40TB ($51.00/usable TB) 5 items across 2 listings. In-stock listings only. Anything out of stock when this page loaded is named below rather than silently dropped.
| Item | Qty | Each | Line | |
|---|---|---|---|---|
| DriveMDD 20TB SATA 7200RPM NAS (20TB) | x4 | $509.99 | $2039.96 | Buy |
| ChassisUniFi UNAS Pro 4 4-Bay | x1 | $699.00 | $699.00 | Buy |
| Basket total | $2738.96 | |||
These are our current tracked prices. Amazon sets the seller and the final price at checkout - verify before you buy. Opening any item starts an Amazon session, and anything you add there is part of the same order - you do not need to come back here between items.
Enterprise fill - UNAS Pro 4 + 4 drives
Usable capacity by RAID level: RAID 1 12TB ($110.00/usable TB) · RAID 5 36TB ($36.67/usable TB) · RAID 6 24TB ($55.00/usable TB) · RAID 10 24TB ($55.00/usable TB) 5 items across 2 listings. In-stock listings only. Anything out of stock when this page loaded is named below rather than silently dropped.
| Item | Qty | Each | Line | |
|---|---|---|---|---|
| DriveWD Ultrastar 12TB SATA HUH721212ALE601 (12TB) | x4 | $329.99 | $1319.96 | Buy |
| ChassisUniFi UNAS Pro 4 4-Bay | x1 | $699.00 | $699.00 | Buy |
| Basket total | $2018.96 | |||
These are our current tracked prices. Amazon sets the seller and the final price at checkout - verify before you buy. Opening any item starts an Amazon session, and anything you add there is part of the same order - you do not need to come back here between items.
Refurbished fill - UNAS Pro 4 + 4 drives
Usable capacity by RAID level: RAID 1 2TB ($76.00/usable TB) · RAID 5 6TB ($25.33/usable TB) · RAID 6 4TB ($38.00/usable TB) · RAID 10 4TB ($38.00/usable TB) 5 items across 2 listings. In-stock listings only. Anything out of stock when this page loaded is named below rather than silently dropped.
| Item | Qty | Each | Line | |
|---|---|---|---|---|
| DriveToshiba MG03ACA200 2TB SATA Enterprise (2TB) | x4 | $38.00 | $152.00 | Buy |
| ChassisUniFi UNAS Pro 4 4-Bay | x1 | $699.00 | $699.00 | Buy |
| Basket total | $851.00 | |||
These are our current tracked prices. Amazon sets the seller and the final price at checkout - verify before you buy. Opening any item starts an Amazon session, and anything you add there is part of the same order - you do not need to come back here between items.
The smallest cheque that fills all 4 bays, separately from the value tiers above: 4 x Toshiba MG03ACA200 2TB SATA Enterprise at $104.98 each = $419.92.
Where the UNAS Pro 4 sits in Ubiquiti's own line
Ubiquiti's techspecs page frames the UNAS Pro 4 as the four-bay member of a wider UNAS Pro family sized by bay count, distinguishing it from consumer-oriented UniFi Drive products by its rack-friendly form factor and its pair of 10G SFP+ ports rather than RJ45-only networking. The 150W power budget figure Ubiquiti publishes splits into a stated 125W specifically reserved for drives, which is the number worth checking against four spinning drives' combined published draw before assuming headroom exists for anything else.
Drive requirements, as Ubiquiti documents them
Ubiquiti's own pages state only generic drive requirements - "3rd-Party Qualified HDD/SSD" and the 2.5/3.5-inch form-factor line - not a named list of approved models the way Synology publishes one per machine. That is a documented posture in its own right (requirements, not a list), matching Ubiquiti's general position across its UniFi storage line.
117 SATA HDDs in our own catalogue are fit-verified for this class of bay right now (interface, form factor and CMR-confirmed) - our own check, not a Ubiquiti claim.
UniFi drive requirements, in full.
Expansion limits and the M.2 reality
We found no vendor-documented expansion unit for the UNAS Pro 4 - four bays is the ceiling for this chassis in what Ubiquiti publishes.
The M.2 slots are unambiguous here, which is worth contrasting with the UGREEN and QNAP pages in this cluster: Ubiquiti's own store page labels the two M.2 slots "cache slots" specifically, with no mention anywhere of an independent storage-pool option. There is no cache-versus-pool decision to make on this model - the vendor documents one role only.
That single-role clarity mirrors Ubiquiti's overall posture on this machine: generic, plainly-stated requirements rather than a named list or a hedged feature description. A buyer choosing between the UNAS Pro 4 and the UGREEN or TerraMaster units in this cluster is choosing, among other things, between that single-purpose M.2 cache and the other two vendors' own claim of an additional independent-pool option - a real difference in what the same two slots can do, not a difference in build quality.
What else it needs
Power protection: see UPS units for a NAS, priced live with output waveform stated on every row. The UNAS Pro 4's two 10G SFP+ ports need matching switch ports and transceivers or DAC cabling - see the 25/40/100GbE hub for live SFP+ networking prices.
Frequently asked questions
Frequently asked questions
How many drives does the UNAS Pro 4 take?
4 bays, 2.5-inch or 3.5-inch HDD or SSD, per Ubiquiti's own techspecs page - plus 2 M.2 NVMe slots specifically labelled as cache slots.
What's the maximum capacity of the UNAS Pro 4?
Ubiquiti publishes no maximum single-drive capacity for the main bays. For the M.2 cache slots specifically, Ubiquiti's own techspecs page states a maximum NVMe capacity of 4TiB.
Does Ubiquiti publish an approved drive list for the UNAS Pro 4?
No - Ubiquiti's own pages state only a generic "3rd-Party Qualified HDD/SSD" and the form-factor requirement, not a named list of approved models. This differs from Synology's per-machine registry - it is an absence, not a documented restriction.
Are the M.2 slots on the UNAS Pro 4 cache-only?
Yes, per Ubiquiti's own store page, which labels them explicitly: "(2) M.2 NVMe SSD cache slots." Neither Ubiquiti page we found describes an independent M.2 storage-pool option for this model - a genuine difference from UGREEN's DXP4800 Plus, whose M.2 slots UGREEN documents as supporting both roles.
What does a complete UNAS Pro 4 build cost?
$699.00 for the chassis alone; $2039.96 filled with 4 best-value drives, or as little as $419.92 for the smallest qualifying set.
What network ports does the UNAS Pro 4 have?
Two 10G SFP+ ports and one Gigabit RJ45 port, per Ubiquiti's own techspecs page.
Sources checked: Ubiquiti UNAS Pro 4 technical specifications, Ubiquiti UNAS Pro 4 store page.