Source? Interested in learning more about this

Red Hat OpenShift (IBM) is what a lot of banks have settled on. Red Hat went all in maybe 5+ years ago in capturing those institutions.

Ah, that explains why IBM bought RedHat. Or at least one reason for doing so.

I'd imagine close to 95% in the US, if they're running important workloads on prem on Linux, it's on RHEL. A staggering number of VMs and bare metal.

(Clarification: I'm not saying 95% of all US company Linux workloads are RHEL, not even close.

I'm saying a huge percentage of high criticality (risk of loss of life / high financial risk) are, simply because of support and the name.)

Exactly. The exact opposite of the people flogging internet widgets running on a bunch of AWS instances running Arch/Ubuntu/Cheap distro of the week. Unfortunately that contingent is massively over-represented here on HN.

Is that in addition to mainframes or for completely replacing them?

Probably both, to respond to the risk tolerances of any given org.

Both

Some stayed at on prem, some pushed code to mainframe VMs in the cloud, some went to OpenShift (mostly on prem from what Ive seen, probably 80-85%).

I work in banking. We provide modern solutions for small local banks in the US. That's how our core runs. It's just Java apps (Spring Boot, Jakarta EE) running in the cloud.

That post fails to mention Capital One's move from IBM mainframes to AWS was one of the reasons they suffered one of the largest data breaches in history.

And what was the financial cost of this?

At least $270,000,000 in direct costs [0].

[0] https://www.security.org/identity-theft/breach/capital-one/

Current generation of banking software is expanding on the mainframe:

IBM Z mainframes play a pivotal role in facilitating 87% of global credit card transactions, nearly $8 trillion in annual payments, and 29 billion ATM transactions each year, amounting to nearly $5 billion per day. Rosamilia highlighted the continuous growth in demand for capacity over the past decade, which has seen inventory expand by 3.5 times.

https://thesiliconreview.com/2024/04/ibm-new-mainframe-web-t...

That's true, but the proportion is shrinking.