Building the System/360 Mainframe Nearly Destroyed IBM

The successor IBM Mainframes are still alive... for the time being.

https://www.redbooks.ibm.com/redbooks/pdfs/sg248329.pdf

oh, they'll stay around for another while.

they also moved on three more CPU generations since that redbook, to z17.

I think it's Linux on Z that makes it sexy and keeps it young, in addition to a number of crazy features, like a hypervisor that can share CPUs between tenants, and a hardware that support live migration of running processes between sites (via fibre optic interconnect) and the option to hot swap any parts on a running machine.

It's doing a number of things in hardware and hypervisor that need lots of brain power to emulate on commodity hardware.

_and_ it's designed for throughput, from grounds up.

Depending on your workload there may be very good economical reasons to consider a mainframe instead of a number of rack-frames.

I suspect the main reason isn't just strictly economical. If you are Google or some such you can probably compensate by building smart software around commodity hardware, but most companies simply can't. Even if they have boatloads of money (banking, insurance) and can hire expensive talent, they simply can't successfully complete such an undertaking because they don't have it in their DNA, and management isn't incentivised to take on such a risky project.

In this case they will just use a mainframe, even it isn't cheaper in the long run.

Thing is Google does not use commodity hardware for their DCs as far as I can tell. They got famous for that back in the early 2000s but I think they abandoned that approach a long time ago.