From: andrew@carrierdetect.com   
      
   On 17/09/2025 00:25, David Wade wrote:   
      
   > Interesting point. So LPARS are physical partitioning. I guess almost a   
   > type-0 hypervisor. You can't over commit. However its part of the   
   > hardware so basically "free". Given you get a minimum of 68 cores in any   
   > current Z box it isn't usually a problem. If you need to over-commit   
   > then you can buy zVM a type-1 hypervisor which is really a re-badged VM/   
   > XA from the 1970s.   
      
   My understanding was that LPARs as configured using PR/SM are logical   
   resources in terms of CPU, managed using using a derivative of VM   
   integrated at firmware level, hence not physical partitioning as I'd   
   understand it (such as how a Sun E10K manages this).   
      
   A quick search turned up IBM documentation which has the line "Shared   
   Logical CPUs assigned to LPARs":   
      
      
   https://www.ibm.com/docs/en/zp-and-ca/3.1.0?topic=simulation-cecs-prsm-lpars   
      
   Well, just the name "Logical" suggests not physical partitioning.   
      
   Happy to be corrected. It's not my area of expertise and keen to improve   
   my understanding.   
      
   Andrew   
      
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