> What is Google's or Facebooks uptime?

99.9 percent. Cloud services from Microsoft, Google, Amazon typically have only three nines or less for paying customers. They also seem to have same level of uptime in their own services.

But these are not "firm guarantees". For example Amazon just gives service credits after downtime exceeds what is promised. They "undergo unscheduled outages" from time to time. Whole regions are down at once.

Remember Amazon's Prime Day outages? It's not good for business when tings go down.

For workloads where eventually consistent is okay.

It's harder to get mainframe like uptimes for OLTP simultaneously with mainframe like IOPS.

Banking uses eventual consistency all over the place. Unsurprising given they started with letters going by ship and courier.

Exactly, I think that folks forget that ATMs operate like that, if the network is down ATM doesn't stop working. That's why folk's account can go below $0. Banks have been operating distributed systems with eventual consistency for a very long time.

Three 9s vs Five 9s. The mainframe wins here. Heck I remember moving a system for a bank that had been up for 23 years.

the scope of the comparison was to a single rack, not all of Google or Facebook.

And even then, what is their non-degraded uptime? There are parts of their infrastructure failing all the time being routed around by incredibly clever software.

And I bet all that costs much more than an IBM. Not a computer, the company.