Drive bays per device, CMR vs SMR, and retention maths done honestly — which means showing you the variables rather than handing you a number.
Specs verified 16–17 July 2026 against techspecs.ui.com. Every figure on this page is Ubiquiti’s own published number. Where Ubiquiti publishes nothing, this page says “Not published” rather than estimating. Contact AVNFi to have a design checked.
UNVR
UNAS Pro
UDM-Pro-Max — two bays
← Storage and Retention is the simple version of this page. It answers “how many days will I get”. This one shows why that answer is a range.
The thing to know before anything else
Ubiquiti publishes no retention formula. No per-camera bitrate. No days-per-terabyte table. No GB-per-hour figure. Nothing.
Therefore every retention number you have ever been quoted — by us, by a forum, by a calculator, by Ubiquiti’s own sales material — is an estimate. Not a specification. An estimate, built on assumptions somebody made and usually didn’t show you.
This page shows you the assumptions. It does not pretend the output is a spec.
Why there is no formula: Protect uses variable-bitrate H.264/H.265 encoding. A camera watching a still hallway and the same camera watching a parking lot in a snowstorm produce wildly different amounts of data from identical settings. Motion is data. A formula that ignored scene content would be precise and wrong, which is worse than a range that is honest.
Where footage can go
Three options, and they are not equivalent.
| Where | What it is | The catch |
|---|---|---|
| Inside a gateway | A drive bay or NVMe slot in the UDM/UCG itself | Capped by the gateway’s Protect camera ceiling and by how big a drive fits |
| A standalone recorder | UNVR / UNVR-Pro | We hold no spec rows for these. See the gap note below. |
| A UNAS | UNAS Pro — network attached storage | A NAS, not a Protect recorder. Different job. |
Drive bays and Protect ceilings, per gateway
| SKU | Name | Drive bays | Other NVR storage | Records Protect natively? | Max Protect cameras (HD / 2K / 4K) |
|---|---|---|---|---|---|
| UDM-Pro | Dream Machine Pro | (1) 3.5″ NVR HDD bay | Not published | Yes | (24) HD / (14) 2K / (8) 4K |
| UDM-Pro-Max | Dream Machine Pro Max | (2) 3.5″ NVR HDD bays | Not published | Yes | (50) HD / (25) 2K / (15) 4K |
| UDM-SE | Dream Machine Special Edition | (1) 3.5″ NVR HDD bay | Not published | Yes | (24) HD / (14) 2K / (8) 4K |
| UDM-Beast | Dream Machine Beast | (2) 3.5″ NVR HDD bays | Not published | Yes | (100) HD / (60) 2K / (40) 4K |
| UDR | Dream Router | None | Not published | Yes | (5) HD / (2) 2K / (1) 4K |
| UDR7 | Dream Router 7 | None | Not published | Yes | (5) HD / (2) 2K / (1) 4K |
| UX | UniFi Express | None | Not published | Not published as Protect-capable | Not published |
| UX7 | UniFi Express 7 | None | Not published | Not published as Protect-capable | Not published |
| UCG-Ultra | Cloud Gateway Ultra | None | Not published | Not published as Protect-capable | Not published |
| UCG-Max | Cloud Gateway Max | Selectable NVMe SSD up to 2 TB | Not published | Yes | (15) HD / (8) 2K / (5) 4K |
| UCG-Fiber | Cloud Gateway Fiber | Selectable NVMe SSD up to 2 TB | Not published | Yes | (15) HD / (8) 2K / (5) 4K |
| UCG-Industrial | Cloud Gateway Industrial | None | Pre-installed 128 GB microSD for NVR; MicroSD expansion slot | Yes | (15) HD / (8) 2K / (5) 4K |
| EFG | Enterprise Fortress Gateway | None | Not published | Not published as Protect-capable | Not published |
| EF-Core | Enterprise Firewall Core | None | Not published | Not published as Protect-capable | Not published |
| UDR-5G-Max | Dream Router 5G Max | None | Pre-installed 64 GB microSD for NVR; MicroSD expansion slot | Yes | (5) HD / (2) 2K / (1) 4K |
Read those two columns together, because they fail in different orders.
- UDR and UDR7 — Protect-capable at (1) 4K camera, and no drive bay and no NVR storage published at all. One camera, total, onto storage Ubiquiti doesn’t describe.
- UCG-Max and UCG-Fiber — “Selectable NVMe SSD up to 2 TB”. That is a real published ceiling: 2 TB, and no more, ever. Five 4K cameras onto at most 2 TB.
- UDM-Pro and UDM-SE — (1) 3.5″ NVR HDD bay. Eight 4K cameras onto one drive you choose.
- UDM-Pro-Max — (2) 3.5″ bays, fifteen 4K.
- UDM-Beast — (2) 3.5″ bays, forty 4K.
- UX, UX7, UCG-Ultra, EFG, EF-Core — no drive bays and no NVR storage published.
Two gateways record to microSD instead of a bay, and this is easy to miss because the drive-bay column is empty for both:
- UCG-Industrial — pre-installed 128 GB microSD, with a microSD expansion slot. Protect-capable at 5× 4K.
- UDR-5G-Max — pre-installed 64 GB microSD, with a microSD expansion slot. Protect-capable at 1× 4K.
A 64 GB microSD is not a retention strategy. Both of these record video and neither takes a real drive. Read “records Protect natively = Yes” together with the storage column, always — the UDR-5G-Max is genuinely Protect-capable and will hold a trivial amount of footage. That is not a criticism of the product; it is a 5G router that can also watch a door. Just don’t buy it as a recorder.
The step that matters is UCG-Fiber → UDM-Pro, and it is a bay, not a speed. Below it you record 1–5 4K cameras onto at most a 2 TB SSD shared with the gateway’s own operating system. From it up you record 8–40 onto a 3.5″ surveillance drive you size yourself. Everything else in the gateway decision is downstream of that.
Drives are not included with any of them. A UDM-Pro arrives as an empty bay.
The recorder gap — stated plainly
Our spec file holds no rows for the UNVR, ENVR or UNVR-Instant. No drive bay count, no capacity ceiling, no power figure, no temperature rating.
We have a cart-verified price for the UNVR ($399 + $31 = $430 all-in) and no specs for it. That is an uncomfortable combination and we would rather say so than paper over it.
What this means practically: if your design turns on exactly how many bays a UNVR has or what its maximum drive size is, do not take that number from this wiki. Ask us and we will read it off Ubiquiti’s page live. We will not reconstruct it from memory.
CMR vs SMR — the one drive spec that will bite you
This is the most consequential thing on this page that has nothing to do with Ubiquiti.
| CMR (Conventional Magnetic Recording) | SMR (Shingled Magnetic Recording) | |
|---|---|---|
| How it writes | Tracks side by side, independently | Tracks overlapping like roof shingles |
| Rewriting a block | Writes it | Must read and rewrite the surrounding band |
| Sustained random write | Consistent | Collapses once the cache fills |
| Cost per TB | Higher | Lower |
| Right for surveillance? | Yes | No |
Why it matters specifically for cameras. A surveillance recorder does exactly the one thing SMR is worst at: continuous, simultaneous, never-stopping writes from many streams at once, forever. There is no idle window for an SMR drive to do its housekeeping, because the cameras never stop.
What it looks like when it goes wrong is the nasty part. It does not fail on day one — it benchmarks fine, copies files fine, and installs fine. It fails weeks later, under load, when the cache is exhausted and every camera is writing at once. Which is to say: it fails on the night something happens.
Buy CMR. Buy drives sold as surveillance drives. WD Purple, Seagate SkyHawk and the equivalents exist for this reason: CMR, rated for 24/7 duty, and rated for many simultaneous streams. A desktop drive at the same capacity is cheaper and is the wrong tool.
Manufacturers have been caught shipping SMR without labelling it. You cannot always tell from the box. This is the single best reason to buy a drive from the surveillance line rather than by capacity and price.
UNAS-Pro publishes a separate “3rd-Party Qualified HDD/SSD” tab on its store page. We have not captured it. If you are buying drives for a UNAS, read that list — it is Ubiquiti’s own qualification and it beats any advice on this page.
The retention maths — the actual variables
The formula everyone wants is:
days = drive capacity / (total bitrate × seconds per day)That is arithmetic, not a specification. The whole difficulty is that Ubiquiti publishes none of the inputs. Here is what each variable actually does.
1. Camera count — linear, and the only obvious one
Double the cameras, halve the days. This is the variable everyone accounts for and it is the least interesting.
2. Resolution — the biggest single lever
Ubiquiti’s own gateway spec rows tell you the ratio without saying so out loud. The UDM-Pro publishes “(24) HD / (14) 2K / (8) 4K”. Same box, same budget, three answers — a 3:1 spread between HD and 4K. That ratio is Ubiquiti’s own published figure and it is the closest thing to a bitrate hint in the entire catalogue.
Almost every camera in the current range is 8MP. See the camera matrix. The 4K column is your column.
3. Frame rate — linear-ish, and the cheapest lever nobody pulls
Published maximums vary more than people expect: 30 FPS on most cameras, 24 FPS on the G6 Pro 360 and AI Multi Sensor 4, 20 FPS on the G6 180, 3 FPS on both Entry models’ package cameras.
Halving frame rate does not halve the file, because inter-frame compression is already exploiting similarity between frames — but it moves it a long way. Going from 30 to 15 FPS on a camera watching a fence line costs you almost nothing you would ever use and buys you a large fraction of your retention back. This is the lever we reach for first.
4. Motion vs continuous — the largest multiplier, and the one with a real cost
Continuous recording writes 24 hours a day, every day, forever. Motion-only recording writes when something happens.
On a quiet interior camera the difference is enormous — a corridor that sees people for two hours a day might write a small fraction of what continuous would. On a busy street-facing camera the difference collapses toward nothing, because the street is always moving. A tree in the wind is motion. Snow is motion. Headlights at night are motion.
The honest trade: motion-only recording buys retention by not recording things. The event you eventually need might be in the gap — the thing that happened just before the detection triggered, or the thing that didn’t trigger it. Continuous plus a shorter retention window is often the better answer than motion-only plus a longer one, and it is nearly always the better answer on the camera that covers your actual entrance.
5. Scene content — the variable that ruins every calculator
Two identical cameras, identical settings, one pointed at a wall and one at a car park. The car park writes several times more data. No calculator on earth knows which one you have.
This is why we give ranges. Anyone giving you a single number for retention is either quoting continuous-at-max-bitrate as a worst case — which is defensible and should be labelled — or guessing at your scene, which is not.
How we actually size storage
Backwards, from the requirement.
- Ask how many days you need, and why. “As many as possible” is not a requirement. An insurance condition, a shift pattern, or “we notice things about a fortnight late” are all real requirements. A fortnight is the answer more often than people expect.
- Assume continuous, not motion. Size for the pessimistic case, then let motion-only be headroom rather than a load-bearing assumption.
- Assume the published maximum resolution and frame rate, then decide deliberately where to turn them down.
- Buy the biggest CMR surveillance drive the bays take, because the drive is a fraction of the job and the second visit to swap it is not.
- Check the bay count before the camera count. A UCG-Max’s 2 TB SSD ceiling is a harder limit than its five-camera ceiling.
- Then tell you it’s an estimate, because it is.
The one line worth remembering: your retention is decided by the drive bay, and the drive bay is decided by the gateway you bought on day one. It is the least reversible decision in the system. Everything else can be added later.
Related
- Storage and Retention — the simple version: how many days
- Choosing a Gateway — the bay decision, in plain English
- Gateways and switches: full tables — every bay and ceiling published
- Cameras: the full spec matrix — the resolutions and frame rates you’d be storing
- Glossary — CMR, SMR, NVR, NAS, defined once
Drive bay and camera ceiling figures from techspecs.ui.com, captured 2026-07-16. CMR/SMR is general storage engineering, not a Ubiquiti spec, and is labelled as such. Retention estimates are estimates — Ubiquiti publishes no formula. AVNFi, Calgary.