IT 3300 : Proxmox

Proxmox VMS

VM creation

More about vms

  • Run using QEMU (Quick Emulator)
    • Hardware emulation (Full VZ)
    • From the perspective of the host system where Qemu is running, Qemu is a user program which has access to a number of local resources like partitions, files, network cards which are then passed to an emulated computer which sees them as if they were real devices.

QEMU vs KVM

You may sometimes encounter the term KVM (Kernel-based Virtual Machine). It means that Qemu is running with the support of the virtualization processor extensions, via the Linux kvm module. In the context of Proxmox VE Qemu and KVM can be used interchangeably as Qemu in Proxmox VE will always try to load the kvm module. (Proxmox handbook)

Emulated vs paravirtualized

See Proxmox handboork 10.1

Image formats

  • QEMU disk image allows CoW, snapshots, and thin provisioning.
  • raw disk image is a bit by bit copy, no thin provisioning or snapshots, but may be faster
  • Vmware image format, only good if you are planning to import/export to vmware

Add: Hard Disk

  • Caching: typically no caching gives best performance, but this setting relates to how the host system will relay information back to the guest when a write operation takes place.
  • Discard: If thin provisioning is supported, when you delete a file, the blocks are marked as empty and your corresponding disk image shrinks.
  • Advanced -> emulate ssd
  • Add a few extra disks to a vm

CPU considerations

IF you set the CPU to 'host' the VM CPU will have the same set of flags as the host CPU.

If you want to do a live migration of VMs between different hosts, your VM might end up on a new system with a different CPU type. If the CPU flags passed to the guest are missing, the qemu process will stop. To remedy this Qemu has also its own CPU type kvm64, that Proxmox VE uses by defaults.

MISC

  • Default is SeaBios, can change to OVMF if you want UEFI boot.
  • See options of VM, can change:
    • boot order
    • start at boot
    • etc...

Clones

  • Full clone: a full copy of existing machine, usually much slower than a linked clone
  • Linked Clone: a writable copy whose initial contents are the same as the original data. Creating a linked clone is nearly instantaneous, and initially consumes no additional space. Think pointers! Copy-on-write. Must first convert to a template (read-only copy)

Other

You can import disk images (or vms exported from another environment) assuming they are in the correct format. But, things might fail depending on how hardware was virtualized.