And incidentally all documentation recommends not extending your LPARs beyond what is available on a single CPC-"node" (see [0]-2-23 for a nice (and honest...) block-diagram). If you extend your LPAR across all CPCs I doubt that many of the HA and hotswap-features continue to work (also there is bugs...). E.g.: you won't hotswap memory when it's all utilized: > Removing a CPC drawer often results in removing active memory. With the flexible memory option, removing the affected memory and reallocating its use elsewhere in the system is possible.

So while you can have single-system-images on a relatively large multinode setup I doubt many people are doing that (at the place I know, no LPARs have TB of memory...). Also in the given price-range you easily can get SSI-images for Linux too: https://www.servethehome.com/inventec-96-dimm-cxl-expansion-...

If you don't need the single-system-images, VMWARE and Xen advertise literally the same features on a blade chassis minus redundant hardware per blade, which is not really necessary when you just migrate the whole VM...

Also if you define the whole chassis as having 120% capacity, running it at 100% capacity becomes trivial too. And this is exactly what IBM is doing keeping around spare CPUs and memory in all setups spec'ed correctly: https://en.wikipedia.org/wiki/Redundant_array_of_independent...

You are right though that the hardware was and is pretty cool and that kind of building for reliability has largely died out. Also up until ARM/Epyc arrived maximum capacity was over-average, but that is gone too. Together with the market-segment likely not buying for performance I doubt many people today are running workloads which "require" a mainframe...

[0] https://www.redbooks.ibm.com/redbooks/pdfs/sg248951.pdf