I also think the very mature caching systems in z/VM and in mainframe DASD farms reduce 'overhead' for virtual machines.
One more question for the VMWare vs z/VM debate: What is your virtualization ratio (number of VMs per real engine)? /Tom Kern ----- Original Message ---- From: Alan Ackerman <[EMAIL PROTECTED]> To: [email protected] Sent: Thursday, October 30, 2008 7:25:17 PM Subject: [IBMVM] I/O Overhead - z/VM versus VMWARE I got asked: “Does z/VM impose non-insignificant overhead? Is it similar to VMware, in which virtual I/O imposes significant overhead, but most processor and memory access runs at close to native physical speed?” I don’t know anything about VMWARE so I could not answer the question. I know that CCW Translation in VM costs significant cycles. I think FCP disks < dedicated DASD < fullpack minidisks < small minidisks. I would HOPE that the zSeries, with so much of virtualization built into the hardware, would have lower costs than VMWARE, but I don’t really know. Any takers? Are there any web sites that give performance comparisons VM versus VMWARE? Alan Ackerman Alan (dot) Ackerman (at) Bank of America (dot) com
