Specifically to your question, I have been using a Dell Precision T3500 (8Gb memory) as an Ignition Gateway with MySQL on Ubuntu 12.04 for 9 months or so. This one has about 4000 tags to 3 controllers (ControlLogix, CompactLogix and Modicon), database connections to both the local MySQL and corporate MSSQL databases, and typically 6 clients. It’s running about 2-3% CPU utilization for Ignition, so I think it’s safe to say that it could do a lot more…