On Mon, Oct 16, 2017 at 08:56:28PM -0400, Jamon Camisso via talk wrote: > ESXi and Xen are 'type 1' hypervisors, in that they are their own > operating system. Guests sit directly on top. VMs need to be patched to > make use of the hypervisor's ability to use virtualization related CPU > instructions. > > KVM, VirtualBox, and Hyper-V (I think) are considered type 2. They run a > normal OS, and then provide an emulation layer for guest VMs. You can > run normal processes on the host OS, because it is just running an extra > set of processes to provide virtualization to guests. The guests don't > need to be modified at all, which is why it is easy to run any OS on a > type 2 hypervisor.
Most guests run fine unmodifed on ESXi so that really has nothing to do with it. And hyper-v requires guests that explicitly support it if you want to run a gen2 hyper-v rather than the original gen1. So type 1 or 2 has nothing to do with the guest being modified or not. xen I believe requires guests that are xen compatible, while kvm does not require it (and uses qemu to emulate legacy hardware as needed), but kvm can perform better (as can most hypervisors) if the guest is helping and vm aware. So virtualbox, virtualpc and vmware workstation are type 2. kvm is in fact a type 1 (it runs in the OS kernel and uses hardware assistance to implement the virtualization. Being able to run other apps on the host has nothing to do with it). At least IBM says kvm is a type 1 hypervisor and they have been doing virtualization probably longer than anyone else. Hyper-v is also a type 1 hypervisor. The distinction isn't really that clear in a lot of cases these days. Certainly if it is a dedicated hypervisor OS, like xenserver or esxi, it is obviously type 1 and if it runs purely as an application like vmware workstation, virtualpc and virtualbox, then it is clearly type 2. If it runs built into an otherwise general purpose OS like hyper-v and kvm, well that it becomes less obvious, although apparently at least IBM (and some others) say that because of the direct hardware access, they are type 1, and essentially are just hypervisors with a lot of extra capabilities outside the virtualization part. > You'll also see the term VMM used interchangeably with hypervisor. > > How the type of VMM relates to device drivers and licensing, I really > can't say. -- Len Sorensen --- Talk Mailing List talk@gtalug.org https://gtalug.org/mailman/listinfo/talk
