System architecture

NVR, VMS or DVR: what is actually recording your cameras

Cameras get all the attention on a quote and the recorder decides most of what the system can do. It is also the part people most often inherit without documentation, from a previous tenant, a previous owner or a previous installer. Here is what the three things are, and which one you are probably running.

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The distinction that matters

Two of them are boxes. One of them is software

The three terms get used as though they were three competing products at the same level, and they are not. A DVR and an NVR are appliances: a box with disks in it whose job is to record cameras. A VMS is software that does the recording and the managing, running on a server, not on a purpose-built box.

The clean way to separate the two appliances is by what arrives at them. A DVR takes an analogue signal, historically down coaxial cable, and digitises it at the recorder. An NVR takes cameras that have already done their own digitising and send it over the network, which is why NVR systems and network cabling arrive together. If you are looking at coax at the camera end, you are looking at the older architecture, whatever the box is called.

A VMS is a different kind of answer. Instead of the recording capacity being a property of a box you bought, it is a property of a server and a licence, which is what makes it the usual answer for estates that are large, spread across sites, or expected to grow in ways nobody can size in advance.

None of this is a ranking. We are not going to tell you a VMS is better than an NVR, because for a single building with a settled camera count it frequently is not, and the extra flexibility is bought with extra complexity that somebody has to look after.

What each answers

Six questions that separate them in practice

Not a feature comparison. These are the questions where the choice actually changes the answer.

How does the system grow?

An appliance grows to the limit of the appliance and then you buy another one. Software grows against the server and the licensing. Where growth is genuinely unpredictable, that difference is the whole argument, and where the camera count is settled it is nearly irrelevant.

How many sites are there?

One building with one recorder is a solved problem in any architecture. Several buildings that need to be looked at as one estate, with one search across all of them, is where a platform answer starts to earn its complexity.

Who has to operate it, and how often?

A system used weekly by one person and a system used daily by a shift of people have different requirements, and the second is where interface quality stops being a preference and becomes whether the thing gets used properly at all.

What else does it have to talk to?

If the cameras have to line up with access control events, or feed a monitoring operator, the integration question is answered at this layer instead of at the camera. That is where the recorder choice has consequences well beyond recording.

Who maintains the underlying platform?

An appliance is largely self-contained. Software on a server means a server, an operating system and updates, and somebody whose job that is. That is a real cost and it belongs in the decision, not in a surprise six months later.

What happens when a camera model is discontinued?

This is the interoperability question, and it is the one nobody asks while everything works. What your recorder or platform will accept decides how bad a discontinued model is, and it is worth knowing before you need to know.

The inherited system

Most buildings did not choose this. They received it

The commonest situation is not somebody picking an architecture. It is somebody who has taken over a building, a lease or a facilities role and found equipment already in place, installed by a company nobody has the details for, holding footage of unknown length, on credentials nobody has.

When that is the position, the useful first move is not choosing between the three. It is establishing what is actually there: which architecture, what the cameras are, where the cable runs, how far back the recording goes, and whether anybody can get material out of it without help. That is a survey and a written record, and it is worth having before any decision about replacing anything.

What tends to come out of it is that the system is neither as good nor as bad as feared. Positions are usually the real problem instead of the recorder, and where an upgrade is right it is often stageable: what is in the walls frequently survives, and pathway is the expensive part. That work is described under CCTV service and repair, which is largely about systems somebody else installed.

If you want to know how far back your own system currently records before anyone visits, that is a check you can do yourself, and how long security cameras keep footage sets out how.

What we will not claim

The parts of this question we refuse to answer generically

That one architecture is inherently more secure. It depends on configuration, on network design and on who has credentials, none of which is a property of the category. Anyone telling you otherwise is selling a category.
How many cameras a given recorder supports. That is a product specification under conditions that are not your building, and it interacts with resolution, frame rate and scene content. We establish it against the actual equipment at survey.
That your existing system needs replacing. Sometimes it does. Frequently the cameras are in the wrong positions and the recorder is blameless, and replacing the recorder fixes nothing you were complaining about.
That a platform will integrate with something before we have seen what you run. We do not promise an integration on the strength of a datasheet, and we do not name a product as supported until it has been checked against your actual equipment.

The interoperability half of that last point has its own page, because it is the misreading that costs commercial buyers the most: what ONVIF does and does not guarantee.

Where this sits

The recorder is one decision inside a design

A recorder choice made before the positions are settled is a choice made without the inputs. How many cameras, at what settings, watching what, and for how long the material has to be kept are all upstream of it, and they are what a survey produces. That sequence is the whole design method described under commercial camera installation.

Two adjacent decisions are frequently confused with this one. What the system notices on its own is a separate capability and lives under video analytics. Whether anybody is watching it while your building is empty is a different purchase again, under remote video monitoring. A recorder does neither of those things by existing.

Two boundaries, as on every page here. We work on commercial premises only and not on private residences. And we do not hold a C-10 or a C-16, so we do not work on fire alarm systems; that is coordinated with your own licensed fire alarm contractor.

Common questions

Recorder and platform questions

Follow the cable at the camera end, which settles it faster than any label. If the cameras are on network cable and the box they land on is a self-contained appliance with disks in it, you are running an NVR. If the cameras are on coaxial cable, you are running a DVR or a hybrid that accepts both, because coax at the camera is the signature of the older architecture. If the recording is done by software on a server, whether that server is in your comms room or somewhere else, and cameras are added through an application, not a box, that is a VMS. The confusing case is a system sold as one thing and built as another, which is common in estates that have been extended twice. Where nobody on site knows, establishing it is part of what we document when we take a system over.

Not automatically, and we would rather say so than sell you an upgrade you do not need. A DVR that is recording the right scenes, holding footage long enough and letting you get material out when you need it is doing its job, and its age is not by itself a fault. The honest reasons to move are specific: you need coverage the existing cameras cannot give at any setting, you cannot get parts, you cannot export usable material, or you are adding positions the system cannot accept. What frequently makes the move cheaper than expected is that existing infrastructure often survives. Coax at camera positions can often carry an IP system over adapters, and existing pathways almost always survive, which means an upgrade is often staged worst-positions-first rather than a rip-and-replace.

It depends entirely on what that platform is conformant to, and it is worth establishing before you buy, not after. Some platforms are built around one manufacturer’s equipment and are genuinely excellent at it while accepting little else. Others accept a wide range of devices through published interoperability specifications. The question to ask is not whether a platform "supports ONVIF" but which named profile it is conformant to, because the guarantee runs between products conformant to the same profile, not between anything carrying the badge. We have written that up separately because it is the misreading that costs people most.

You do, on every job, and we put it in writing at handover. That means the administrator credentials for the recorder or platform, the configuration as built, and the ability to export your own material without going through us. We take the view that a customer who cannot get into their own system does not own it, whatever the invoice says, and a security company holding the only set of credentials to a building’s recordings is a position we will not put you in. If you later move to another integrator, nothing about the system has to be unpicked to let you do it.