I want to love Mainframes that much, but I frigging hate the way enthusiasts are treated by IBM.

As such, and a direct consequence of it, I will never advise my clients to go for anything IBM.

At least you can run Linux on an LPAR (and these machines are ridiculously fast Linux boxes). I wonder how a couple racks of z15 systems would compare to performance-equivalent racks of commodity x86 servers. I suspect that, per watt and area, these machines can host a lot more VMs than commodity racks.

One commercial said it could host 9000 docker containers per lpar. Sounds tempting of course.

But nah. I am not touching it, until IBM gets their ducks in a row.

You can run z/VM under the LPAR and host multiple Linux images under it, or host Linux directly on the LPAR and use KVM to split it into smaller VMs. The penalty for CPU oversubscription seems relatively small with the almost a gigabyte of L4 cache in every processor drawer.

I'm not buying one (sadly it's a bit over my impulse buy threshold), but I'd love to play with one.

The maintenance costs are scary, though. X86 servers are practically a commodity.

I rescued a Multiprise 3000 from a scrap metal dealer. It's seemingly impossible to get the OS/2 Warp software just to be able to bring the mainframe hardware up. I can't even get to the point where I might actually be able to use an OS.

If you've got back up media, you can still get the OS/390 Backup Facility from Arca Noae: https://www.arcanoae.com/shop/s-390-backup-facility/

(Arca Noae is IBM's licensed purveyor of OS/2.)

I don't have anything. It came from a state auction where they "sanitize" storage with hammers.