I read the guide on speccing the server but my project differs from the numbers there
It would comprise of 250k tags of which max 3k would be in historian , all from 1 plc (siemens s7-1518, siemens adressing, plc can handle this load. we already did it with other scada systems) and a maximum of 10 cuncurrent clients
For development we would be working with 4 people at the same time
Right now a spec of 4 cores and 16 gb of ram on new server hardware is mandated by the client
Sales engineering is a lot better at answering questions like this.
4 cores might be okay if they are real cores and not virtualized, but 16gb of RAM seems low. You probably want at least 16gb dedicated to just Ignition, possibly more.
I don't know what polling rates you have in mind but I'm extremely skeptical about this part.
1 sec for most. If there is a reliable way to set a bit in a dword tag the number of tags would go down dramatically.
Also is there a way where tags would go to sleep automatically if if they are not requested by a client or script ? 80% are tags that would be used only in popup windows (settings, setpoints and auto/manual/ start/ stop commands)
If you're not aware of the limitations when using the S7 protocol with the 1200 or 1500 then see "considerations" here: Siemens - Ignition User Manual 8.1 - Ignition Documentation. There is no symbolic addressing or browsing, only raw area/offset by manual tag creation.
but we can go arround it by using UDT in the PLC and providing the start adress in the parameters of the ignition UDT