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>TL;DR: this is timeshared mainframes all over again. The article was reiterating the advantages of virtual machines -- which handles different operating syst

by jasode 12y ago

>TL;DR: this is timeshared mainframes all over again. The article was reiterating the advantages of virtual machines -- which handles different operating systems. I thought the timeshare concept on mainframes was user-&-application-level time slicing and not os-level. (E.g. an IBM 370 does not simultaneously run OS/360 and MVS operating systems in isolation.) Therefore, the closer analogy to mainframe timesharing would be Citrix Xen desktop or Microsoft Remote Desktop Session Host.

KaiserPro 12y ago
THe hypervisor concept is something that IBM invented and shipped with the 360-40. You can run lots of code from the 70's with little to no modification on a z series mainframe, because its visualized. However My analogy is based on the idea the cloud is effectively a mainframe. They are espousing the joys of single application VMs that effectively rely on the host to do the time-sharing. Something very reminiscent of early timesharing OS
- jasode 12y ago
  >You can run lots of code from the 70's with little to no modification on a z series mainframe, because its visualized. Ok, I thought the main mechanism for running old code was instruction-set-compatiblity-mode emulation and not full isolated virtualization. Could you copy an entire OS+app stack as a self-contained disk file from one mainframe to another? Regardless of the z series vm capabilities, I don't think people think of that as "mainframe time sharing" and that's what tripped me up.
  - KaiserPro 12y ago
    yup, pretty much The best part about IBM mainframes was/is that you shouldn't need to worry about copying the OS to keep the App happy. The mainframe OS effectively provides a VM in a similar style to python or java. You tell it what version of machine its supposed to run on and it'll provide an environment with all the quirks. The article goes on to talk about uOS type systems, which are there to provide a Linuxy shim (with all the quirks) between the hypervisor and the App. (do you start to see where I'm going? :) )

by jasode 12y ago

KaiserPro 12y ago

THe hypervisor concept is something that IBM invented and shipped with the 360-40. You can run lots of code from the 70's with little to no modification on a z series mainframe, because its visualized. However My analogy is based on the idea the cloud is effectively a mainframe. They are espousing the joys of single application VMs that effectively rely on the host to do the time-sharing. Something very reminiscent of early timesharing OS

jasode 12y ago
>You can run lots of code from the 70's with little to no modification on a z series mainframe, because its visualized. Ok, I thought the main mechanism for running old code was instruction-set-compatiblity-mode emulation and not full isolated virtualization. Could you copy an entire OS+app stack as a self-contained disk file from one mainframe to another? Regardless of the z series vm capabilities, I don't think people think of that as "mainframe time sharing" and that's what tripped me up.
- KaiserPro 12y ago
  yup, pretty much The best part about IBM mainframes was/is that you shouldn't need to worry about copying the OS to keep the App happy. The mainframe OS effectively provides a VM in a similar style to python or java. You tell it what version of machine its supposed to run on and it'll provide an environment with all the quirks. The article goes on to talk about uOS type systems, which are there to provide a Linuxy shim (with all the quirks) between the hypervisor and the App. (do you start to see where I'm going? :) )