Virtualization

What is Hyperconverged Infrastructure (HCI)

Your resources: compute, storage, networking.

HCI: uses software to abstract, pool and manage those resources. (i.e. just another term for virtualized / software-defined compute, storage and networking.)

• virtualized computing: hypervisor
• virtualized storage: software defined storage (SDS)
• virtualized networking: software defined networking (SDN)

The Virtualization Stack in Linux

• KVM: Linux kernel module that allows a user space program access to the hardware virtualization features of various processors; allows the kernel to function as a hypervisor. KVM itself emulates very little hardware, instead deferring to a higher level client application such as QEMU.
• QEMU: provides a set of different hardware and device models for the machine, supports the emulation of various architectures; can boot many guest operating systems. QEMU = Quick Emulator.
• libvirt: the lib to manage KVM, Xen, VMware ESXi, QEMU.
• virt-manager: using libvirt; included in many linux distros.
• kubevirt: brining VMs to k8s. Using libvirt + QEMU + KVM.

Live Migration

KVM has included LM (Live Migration) for over a decade.

KubeVirt has been supporting Live Migration functionality out of the box since CY2020 (see https://kubevirt.io/2020/Live-migration.html)

Azure: https://docs.microsoft.com/en-us/azure/virtual-machines/maintenance-and-updates

Cloud Init

https://cloud-init.io/

cloud-init is a widely adopted project used for early initialization of a VM. Used by cloud providers such as AWS and GCP, cloud-init has established itself as the defacto method of providing startup scripts to VMs.

It can also be used for generating and setting up SSH private keys.

Solutions

• VMware: losing popularity, especially after its acquisition by Broadcom (price hike, licensing change, etc).
• Microsoft Hyper-V: integrated into Windows Server.
• Nutanix AHV
  hypervisor integrated into the Nutanix hyperconverged infrastructure platform.
• Red Hat Virtualization (RHV): An open-source platform based on KVM, providing enterprise-grade features and support.
• Proxmox VE: An open-source hypervisor combining KVM and LXC containerization.
• Oracle VM VirtualBox: A popular desktop virtualization solution known for its ease of use and cross-platform support.
• Citrix Hypervisor: An enterprise-level hypervisor

Software Defined Data Center (SDDC)

Redfish: specs for APIs.

E.g. Netapp ONTAP: Compute nodes are all RedFish API-compatible.

CR3

In x86, the page table root address of a process is stored in CR3. In VM exit, the content of the cr3 register is stored in the VMCS. A ring buffer can be used to cache cr3 registers for each guest process during VM exit handling.