We do need to account what is required and what is achievable for each use case. We run an ERP system with >250k self-service users on a single beefy database.

We do need to account what is required and what is achievable for each use case. We run an ERP system with >250k self-service users on a single beefy database. There's redundancy in web servers and app servers and proxy servers and whatnot. But in 5+ years and a LOOOOOOT of all kinds of issues -- it's never been that single big LPAR with single big RDBMS that was the issue. And we're not even on a mainframe. And it's not because we got lucky - some single-computer/LPAR/RDBMS stacks simply give us as many 9's as we need for our use-case. (webservers on other hand - they feel like child's toys. I don't understand how these leaky errory cachy things survive... YOU HAVE ONE JOB! And you're not very good at it :P )