10 ms·

Yeah, this whole LPAR thing is supposed to make oversubscribing less of an issue, but in practical terms it is comparable to Xen PV without HVM mode (Essentiall

Yeah, this whole LPAR thing is supposed to make oversubscribing less of an issue, but in practical terms it is comparable to Xen PV without HVM mode (Essentially Vt-i without Vt-d). It's not that it never works, it's just that you have to take severe shortcuts and snowflake kernels to get it to work in the first place (so now you're incompatible with the body of knowledge that is the internet), and then you essentially just do multiproces CPU core sharing, memory sharing with swapping etc... not great.

evol262 5y ago
VT-d is used for device passthrough. I suspect you're thinking of VT-x. But LPAR have been around forever, and aren't that different conceptually from jails, systemd-nspawn, LXC, and any other of a large number of OS-level virtualization solutions, except that you can stub in/out different kernels. Yes, the kernels need to be "snowflakes", but that's not necessarily an issue if this is functionality you really need.
- nix23 5y ago
  LAPR is not a OS-level virtualization, you can install Linux on a LPAR (however you do it normally with z/vm), it's more like a Hard, Hardware divider. https://en.wikipedia.org/wiki/Logical_partition https://en.wikipedia.org/wiki/Logical_partition
  - oneplane 5y ago
    Essentially it's a microcode hypervisor. You can indeed install Linux on an LPAR, but it will be a useless linux unless you intend to use it for classic 'bog box' installations. (with big box referring to the cardboard boxes that come with installation floppies/CD/DVD media type of software 'distribution') While an LPAR could technically be HVM, the nature of the changes required to an OS make it PV-like.
    - nix23 5y ago
      I just wanted to say that it's NOT like jails and it's not OS-Virtualization.
      - oneplane 5y ago
        If someone wanted to make a comparison, it's like additional 'rings' the x86 ring security model, but instead of nested rings it's parallel rings. You might as well have a single OS with containers.
- oneplane 5y ago
  Yes, you are correct, I was thinking about the oldest of the VT's. The one that did accelerate but didn't even require an IOMMU.

evol262 5y ago

VT-d is used for device passthrough. I suspect you're thinking of VT-x. But LPAR have been around forever, and aren't that different conceptually from jails, systemd-nspawn, LXC, and any other of a large number of OS-level virtualization solutions, except that you can stub in/out different kernels. Yes, the kernels need to be "snowflakes", but that's not necessarily an issue if this is functionality you really need.

nix23 5y ago
LAPR is not a OS-level virtualization, you can install Linux on a LPAR (however you do it normally with z/vm), it's more like a Hard, Hardware divider. https://en.wikipedia.org/wiki/Logical_partition https://en.wikipedia.org/wiki/Logical_partition
- oneplane 5y ago
  Essentially it's a microcode hypervisor. You can indeed install Linux on an LPAR, but it will be a useless linux unless you intend to use it for classic 'bog box' installations. (with big box referring to the cardboard boxes that come with installation floppies/CD/DVD media type of software 'distribution') While an LPAR could technically be HVM, the nature of the changes required to an OS make it PV-like.
  - nix23 5y ago
    I just wanted to say that it's NOT like jails and it's not OS-Virtualization.
    - oneplane 5y ago
      If someone wanted to make a comparison, it's like additional 'rings' the x86 ring security model, but instead of nested rings it's parallel rings. You might as well have a single OS with containers.
oneplane 5y ago
Yes, you are correct, I was thinking about the oldest of the VT's. The one that did accelerate but didn't even require an IOMMU.