IP.21 is a superior historian backend but its certainly more expensive in probably all cases. I’m also talking pure historian here. Ignition is incredible value for the price in my estimation but there are better products if price is not an issue.
Pulling in trends into Ignition with IP.21 backend is possible via ODBC adapter for sure as I did that in several cases but its not a first class experience but definitely do able on a windows box. Not sure about via linux and jdbc or via OPCUA interfaces. Not sure I’d recommend it unless you had the infrastructure in place and wanted to keep IP.21.
We used the Ignition Tag History aspect in a standalone project with probably up to 200,000 realtime tags available at 1-3 second updates (not all continuously updating on screens) and probably 10,000 continuously logging historian tags at about every 3 seconds. Exporting data to CSV was the hardest part requiring jython custom scripts to meet our needs since existing tools didn’t quite meet our needs at the time.
Ignition performed reasonably ok for us with very little maintenance over 3-4 year span. Most operational problems were with mysql once the initial bugs were shaken out and that was mostly non-issue. Though we did have some issues with tag updates breaking a couple hundred historical tags in the project in a way we never resolved. How Ignition handled import of tags a few years ago was a bit of pain for us but that may have been improved.
We used mysql for the historian and a server with 2 TB of storage. With this trends worked well and HMI displays were easy to develop. There was no equivalent of Process Explorer for operator to use where they could define their own chart with own points list out of the box so there was a bit of custom work to make dynamic trends in displays but it was possible which is testament to Ignition’s flexibility.