How is a Historian Different from an Edge Gateway?

Summary: What is the difference between an industrial Historian and an Edge Gateway? While both handle factory data, their primary functions differ:

• An edge gateway acts as a real-time router, normalizing and publishing data to cloud or Enterprise applications
• A historian is a specialized database designed for long-term storage, high-frequency ingestion, and forensic analysis.
• This guide breaks down the features, limitations, and use cases for both edge gateways and historians.

What is the Difference Between a Historian and an Edge Gateway?

A historian and an edge gateway look similar, talk similar, and promise to provide data to your applications, but choosing the wrong one is like hiring a librarian to fly a fighter jet. It’s not going to end well.

The table below compares the core features of the two solutions, illustrating that edge gateways are for publishing data and historians are for long-term storage and diagnostics.

Dimension	Edge Gateway	Historian
Primary Job	Move, normalize and publish real-time data	Store, index and retrieve historical time-series data
Core Question Answered	“Where does the data need to go right now?”	“What happened, when and why?”
Data Flow Model	Continuous distribution (pub/sub, streaming)	High-throughput ingestion into a time-series database
Typical Destinations	UNS, MQTT brokers, cloud dashboards, ERP, MES	Visualization tools, analytics platforms, compliance reports
Data Retention	Short-term buffering only (store-and-forward)	Long-term retention (months to years)
Latency Priority	Low latency, near real-time	Write speed and consistency over latency
Timestamp Accuracy	Useful but not mission-critical	Critical. Accurate timestamps are essential
Data Modeling / Context	Strong. Adds metadata and structure for consumers	Moderate. Often relies on external context
Analytics Capability	Minimal. Focused on transport	Strong for trends, diagnostics and forensics
Failure Mode Risk	Single point of failure for outbound connectivity	Storage saturation or performance degradation
Security Scope	Designed for IT/OT boundary and cross-zone movement	Designed for in-zone operation and trusted networks
IEC 62443 Role	Often spans zones and conduits	Typically confined to a production zone
Licensing Model	Often hardware-based, sometimes licensed	Frequently licensed by tags, points, or throughput
Best Fit Use Cases	Real-time decision-making, interoperability, UNS	Compliance, root-cause analysis, long-term optimization
Poor Fit Use Cases	Long-term storage or forensic analysis	High-volume real-time data distribution

What is an Edge Gateway?

An edge gateway collects, normalizes and routes data from PLCs, HMIs, drives and other production equipment directly to your cloud or enterprise apps. It prioritizes uptime and speed over long-term storage and is critical to edge computing applications. While most have a “store-and-forward” feature (so you don’t lose data if the Wi-Fi hiccups), they aren’t meant to hold onto that data for years.

You can think of an edge gateway as the frantic, highly efficient air traffic controller of your factory. Its main job isn’t to store the planes; it’s to make sure they get where they’re going without crashing, regardless of what language the pilots are speaking.

What are the “Must-Haves” Features of an Edge Gateway?

1. A Universal Translator: If your gateway can’t talk to that one crusty legacy PLC from 1994 and your shiny new sensors, it’s useless. Multi-protocol ingestion is king.
2. A Filter: You don’t need to send every single millisecond of a steady-state temperature to the cloud. That’s just paying for storage you don’t need. You want a gateway that can scale and filter data locally.
3. Data Modeling (Context is King): Raw data is just numbers. A good gateway adds “metadata.” It doesn’t just send “72.4”; it sends “72.4°C, Tank 4, High-Pressure Line.”
4. Pub/Sub Flexibility: It should speak the languages of the modern world: MQTT (Sparkplug B, please!), OPC UA, REST or even direct SQL injection.
5. The “Grandma Test” Deployment: If it takes three weeks of coding to commission, you’ve bought a headache, not a tool. Look for no-code, web-based configuration.
6. Cybersecurity: If you’re connecting to the internet, you need more than a “keep out” sign. Look for built-in firewalls and encryption, especially if the device sits near the IT/OT line. In terms of the IEC 62443 standard (Technical Security Requirements for IACS Components), you should meet Security Level 3.

What are the Limitations of an Edge Gateway?

• Limited Resources: Edge gateways and devices typically have constrained processing power, memory and storage. If connectivity to the data destination is lost, the limited storage can result in data loss.
• Increased Security Risks: The nature of edge gateways is such that they have a larger “attack surface” for potential threats. Consistent security updates across many remote nodes can be a significant challenge.
• Potential Single Point of Failure: An edge gateway can be a single point of failure. If the gateway fails, local connectivity to the external applications will be lost, possibly impacting operations.
• Integration Challenges: Edge gateways often need to integrate with legacy systems that use outdated or proprietary protocols, sometimes requiring significant engineering effort and specialized interfaces.

What is a Historian?

Historians have one goal: Retention. They take time-series data from your manufacturing system and tuck it away in a database so you can look at it three years from now and say, “Ah, so that’s why the pump failed on a Tuesday.” Historians make data explorable, reusable and ready to scale across your factory.

Where an edge gateway cares about where the data is going, the Historian cares about how much it can hold and how fast it can store data.

What are the “Must-Haves” features for a Historian?

A factory floor Historian should have nearly the same features as an edge gateway – the universal translator, filtering, data modeling and cybersecurity plus:

1. High-Frequency Ingestion: Some processes happen in sub-milliseconds. Some Historians are optimized for that kind of “firehose” data entry without dropping a single packet.
2. Compression: Storing years of data takes up a lot of storage space. Some high-volume historians use smart compression, so your 1 TB drive doesn’t fill up in a week.
3. Timestamping (The “When” Matters): If your Historian’s clock is off by three seconds, your data analytics are fiction. A historian should use protocols such as NTP or PTP to ensure every data point is perfectly synchronized.
4. The Excel Factor: Let’s be honest—most of us eventually want that data in a spreadsheet. A good Historian makes it easy to export to CSV or via API to the “common man’s analytics engine” (Microsoft Excel™).

What are the Limitations of a Historian?

• Suitability Issues: Not all Historians can support the massive volume and the velocity of data from modern IoT devices and sensors.
• Data Silos and Integration Challenges: Factory floor data is often locked in isolated systems with uncommon or unsupported protocols, inhibiting data ingestion and making holistic analysis difficult.
• Limited Advanced Analytics: Many historians lack built-in capabilities for advanced analytics, machine learning integration or real-time processing, limiting their usefulness.
• High Total Cost of Ownership (TCO): Licensing and maintenance fees, especially in software-only deployments, can be high, especially as data volumes grow.
• Data Quality and Context: Ensuring consistent, clean and reliable data is an ongoing challenge. Without a clear framework to relate different data points, users struggle to form a complete understanding of the operational context.

What are the Historian and Edge Gateway Deployment Options?

There are two deployment options: licensed software or a hardware appliance. Licensed software requires an available server or VM. Hardware appliances can be standalone or DIN-rail mounted.

Licensed software options include both on-premise and cloud. These offer regular updates, but the total cost of ownership is higher. Hardware options offer lower total cost of ownership but require cabinet or DIN-rail rack space.

The table below shows historians are the more feature-rich factory floor device.

Recommended Features	Edge Gateway	Historian
In-Zone Operation	N/A	✔
Cross-Zone Operation	✔	✔
Cybersecurity	IEC 62443 SL 2 or 3	IEC 62443 SL 2 or 3
Universal Translator	✔	✔
Normalization, Scaling, Filtering, Aggregation	✔	✔
Store and Forward	✔	✔
High Frequency Ingestion	N/A	✔
Time Stamping	N/A	✔
Publishing	AWS, AZURE, MQTT, OPC UA, SQL INGESTION	AWS, AZURE, MQTT, OPC UA, SQL INGESTION, FTP (CSV/JSON)
Data Compression	N/A	✔

How to Choose a Historian or an Edge Gateway?

It usually comes down to what you plan to do with the data once you have it.

You should choose an edge gateway if you need to move data to a Unified Namespace (UNS), a cloud dashboard or an ERP system for real-time decision-making. You care about connectivity and interoperability.

You should choose a historian if you are in a regulated industry (like Pharma or Food) and need “proof of process” or if you are doing deep-dive forensic analysis on machine failures. You care about history and granularity.

Both historians and edge gateways can function at the edge of the production zone and with sufficient cybersecurity capabilities, they can eliminate the need for a firewall.

The “Why Not Both?” Solution: The Hybrid Approach

In the real world, factory floors are messy. You often need the connectivity of a gateway and the storage of a historian. This is where most people get stuck—buying two separate boxes, two separate licenses and twice the configuration gray hairs.

At Real Time Automation, we looked at that problem and thought, “There has to be a way to make this less painful.” Enter the RTConnect Allen-Bradley PLC Historian.

We essentially took the “best of both worlds” and packed them into one rugged, industrial-grade box. It’s a lightweight, embedded historian that plays like an edge gateway.

Why our Enginerds love it (and you will too):

• It’s Independent: No monthly subscriptions, no “per-tag” licensing fees that bleed your budget dry, and no reliance on third-party middleware.
• Huge Storage: Up to 1 TB of local storage.
• Protocol Powerhouse: It captures data from multiple PLCs and can publish it via SQL, MQTT, FTP, or even Email.

Make Sure Your Data Doesn’t Go Missing

Whether you’re an OEM looking to add value to your machines or a process engineer trying to figure out why Line 3 keeps tripping, your data is your most valuable asset. Don’t let it vanish into the void like the scrolls of Alexandria.

Choosing between an edge gateway and a historian doesn’t have to be a “guess and check” operation. It’s about matching the tool to the task.

Ready to stop guessing? Our team of Enginerds is standing by to help you figure out the exact architecture for your plant. We won’t sell you a library if all you need is a map.

Have questions about your particular application? We’re available if you want to hop on a quick call with one of our experts to audit your current data setup. Give us a shout at 262-436-9299 or drop us an email at solutions@rtautomation.com. Let’s make sure your factory’s history is preserved, not lost.

Historian vs. Edge Gateway Frequently Asked Questions