Virtualization

This guide is intended to explain how virtualization works within Cozystack.

The Cozystack catalog includes three packages related to virtualization:

• virtual-machine - Virtual Machine (simple)
• vm-disk - Virtual Machine disk
• vm-instance - Virtual Machine instance

Virtual Machine (simple)

This package provides a quick way to create a simple virtual machine. It allows you to specify the bare minimum parameters to run a VM, but it only supports a single-disk virtual machine.

For production workloads, it is recommended to use vm-disk and vm-instance instead.

Virtual Machine Disk

Before creating a Virtual Machine instance, you need to create a disk from which the VM will boot.

This package defines a virtual machine disk used to store data. You can download an image to the disk via HTTP or upload it from a local image. You can also create an empty image.

1. HTTP:

   source:
     http:
       url: "https://download.cirros-cloud.net/0.6.2/cirros-0.6.2-x86_64-disk.img"
   

2. Upload:

   source:
     upload: {}
   

   After the disk is created, it will generate a command for uploading using the virtctl tool.

   Note:

   If you want to let virtctl know about right endpoint for uploading images, you need to configure a cluster to specify an endpoint for it:

   1. Modify your ingress application to enable cni-uploadproxy option.

      kubectl patch -n tenant-root ingresses.apps.cozystack.io ingress --type=merge -p '{"spec":{
        "cdiUploadProxy": true
      }}'
      

   2. Modify your cozystack config to provide a valid CDI uploadproxy endpoint:

   values-cdi: |
     uploadProxyURL: https://cdi-uploadproxy.example.org  
   

3. Empty:

   source: {}
   

Optionally, you can specify that the disk is an optical CD-ROM:

optical: true

Created disks can be attached to a Virtual Machine instance.

Virtual Machine Instance

This package defines a Virtual Machine instance, which requires specifying the previously created vm-disk. The first disk is always bootable, and the VM will attempt to boot from it.

disks:
- name: vm-disk-example-system
- name: vm-disk-example-data

The rest parameters are similar to Virtual Machine (simple)

Accessing Virtual Machines

You can access the virtual machine using the virtctl tool:

• KubeVirt User Guide - Virtctl Client Tool

To access the serial console:

virtctl console <vm>

To access the VM using VNC:

virtctl vnc <vm>

To SSH into the VM:

virtctl ssh <user>@<vm>

Virtual Machine Configuration

You can specify instanceType and instanceProfile for the virtual machine.

• instanceType - defines the size for the Virtual Machine.
• instanceProfile - defines the set of preferences for Virtual Machines, according to the OS being used.

You can find more information about these settings below:

U Series

The U Series is quite neutral and provides resources for general purpose applications.

U is the abbreviation for “Universal”, hinting at the universal attitude towards workloads.

VMs of instance types will share physical CPU cores on a time-slice basis with other VMs.

U Series Characteristics

Specific characteristics of this series are:

• Burstable CPU performance - The workload has a baseline compute performance but is permitted to burst beyond this baseline, if excess compute resources are available.
• vCPU-To-Memory Ratio (1:4) - A vCPU-to-Memory ratio of 1:4, for less noise per node.

O Series

The O Series is based on the U Series, with the only difference being that memory is overcommitted.

O is the abbreviation for “Overcommitted”.

UO Series Characteristics

Specific characteristics of this series are:

• Burstable CPU performance - The workload has a baseline compute performance but is permitted to burst beyond this baseline, if excess compute resources are available.
• Overcommitted Memory - Memory is over-committed in order to achieve a higher workload density.
• vCPU-To-Memory Ratio (1:4) - A vCPU-to-Memory ratio of 1:4, for less noise per node.

CX Series

The CX Series provides exclusive compute resources for compute intensive applications.

CX is the abbreviation of “Compute Exclusive”.

The exclusive resources are given to the compute threads of the VM. In order to ensure this, some additional cores (depending on the number of disks and NICs) will be requested to offload the IO threading from cores dedicated to the workload. In addition, in this series, the NUMA topology of the used cores is provided to the VM.

CX Series Characteristics

Specific characteristics of this series are:

• Hugepages - Hugepages are used in order to improve memory performance.
• Dedicated CPU - Physical cores are exclusively assigned to every vCPU in order to provide fixed and high compute guarantees to the workload.
• Isolated emulator threads - Hypervisor emulator threads are isolated from the vCPUs in order to reduce emaulation related impact on the workload.
• vNUMA - Physical NUMA topology is reflected in the guest in order to optimize guest sided cache utilization.
• vCPU-To-Memory Ratio (1:2) - A vCPU-to-Memory ratio of 1:2.

M Series

The M Series provides resources for memory intensive applications.

M is the abbreviation of “Memory”.

M Series Characteristics

Specific characteristics of this series are:

• Hugepages - Hugepages are used in order to improve memory performance.
• Burstable CPU performance - The workload has a baseline compute performance but is permitted to burst beyond this baseline, if excess compute resources are available.
• vCPU-To-Memory Ratio (1:8) - A vCPU-to-Memory ratio of 1:8, for much less noise per node.

RT Series

The RT Series provides resources for realtime applications, like Oslat.

RT is the abbreviation for “realtime”.

This series of instance types requires nodes capable of running realtime applications.

RT Series Characteristics

Specific characteristics of this series are:

• Hugepages - Hugepages are used in order to improve memory performance.
• Dedicated CPU - Physical cores are exclusively assigned to every vCPU in order to provide fixed and high compute guarantees to the workload.
• Isolated emulator threads - Hypervisor emulator threads are isolated from the vCPUs in order to reduce emaulation related impact on the workload.
• vCPU-To-Memory Ratio (1:4) - A vCPU-to-Memory ratio of 1:4 starting from the medium size.

Development

To get started with customizing or creating your own instancetypes and preferences see DEVELOPMENT.md.

Resources

The following instancetype resources are provided by Cozystack:

The following preference resources are provided by Cozystack: