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Description

This article serves as an introduction Advanced Virtualization Settings

Overview

Advanced Virtualization Settings are a series of obscure vSphere configuration settings supported by CloudControl primarily for use in SAP private cloud environments. They exist on both Images and Cloud Servers. In vSphere, these settings are mainly set in the extraConfig named-pair values of a VMX file. 

Currently, the list of supported Advanced Virtualization Settings are:

  • Nested Hardware Virtualization (vSphere nestedHVEnabled)

    • This setting is identified on all Images and Servers and will usually be set to false.

    • When set to true, this setting exposes full CPU virtualization to the Guest Operating system so that applications that require hardware virtualization can run on virtual machines without binary translation or paravirtualization.

  • CPU Latency Sensitivity (vSphere sched.cpu.latencySensitivity)

    • This setting appears on Images and Servers only when explicitly set and will usually not appear. If explicitly set to NORMAL, it behaves identically to not being set at all.
    • When the value is explicitly set to HIGH, vSphere will dedicate physical cores to vCPUs, which significantly reduces execution latency and jitter for that VM.

    • When the value is explicitly set to LOW, vSphere may provide lower performance in terms of latency to the underlying vCPU. We strongly recommend avoiding this setting.
  • NUMA Autosize  (vSphere numa.autosize & numa.autosize.once - CloudControl requires both to be set in tandem)

    • This setting appears on Images and Servers only when explicitly set and will usually not appear. If explicitly set to false, it behaves identically to not being set at all.
    • When explicitly set to true, this setting ensures that a server’s virtual NUMA topology has the same number of virtual CPUs per virtual node as the number of cores on each physical node.

  • Enable Host Info to VM Tools (vSphere tools.guestlib.enableHostInfo)

    • This setting appears on Images and Servers only when explicitly set and will usually not appear. If explicitly set to false, it behaves identically to not being set at all.
    • When explicitly set to true, this setting allows the VM Tools to gather information about the ESXi host

Advanced Virtualization Settings on OS and Client Images

On Images, these settings are visible on the Image Details screen as shown below:

If these Advanced Virtualization Settings appear on an OS or Client Image, the resulting Cloud Server will inherit the same Advanced Virtualization settings when servers are deployed from the image. Users can modify the Advanced Virtualization settings on Client Images as described in How to Manage a Client Image. However, users should review the Restrictions on Advanced Virtualization Settings section below as some settings will prevent use of the image if the Data Center location does not support the restricted setting.

Note that in most cases, Advanced Virtualization settings are not supported by the Import function described at Introduction to the Import / Export Function. Advanced Virtualization settings will be dropped as part of the Import process. Users may need to update the Client Image after importing if they wish to retain settings that may have existed prior to import. The same is true when Client Images are copied between data centers as described in How to Copy a Client Image between Locations in the Same Geographic Region

Advanced Virtualization Settings on Cloud Servers

On Cloud Servers, these settings are visible on the Server Details screen as shown below:

If these Advanced Virtualization Settings appear on a Server:

  • Cloning a Cloud Server to create a Customer Image as described in How to Clone a Cloud Server to Create a Client Image will result an a Client Image that  inherit the same Advanced Virtualization settings.
  • Cloud Server Snapshots (described in Introduction to Cloud Server Snapshots) created from the Cloud Server will inherit the same Advanced Virtualization settings.
  • The DRS for Cloud function (described in Introduction to DRS for Cloud) will not replicate Advanced Virtualization settings from the Source Servers in the Consistency Group. After Snapshot Preview is initiated, users will need to adjust such settings to match the Source server if desired.
  • In addition, when using the DRS for Cloud function, when Creating a Consistency Group, the Target Server cannot have any Advanced Virtualization Settings set regardless of whether these settings are allowed on the Cluster. Certain settings interfere with the proper operation of DRS.

Users can adjust Advanced Virtualization Settings as described in How to Manage a Cloud Server. However, all adjustments are subject to the policies described in the Restrictions on Advanced Virtualization Settings section below

Restrictions on Advanced Virtualization Settings

Most Advanced Virtualization Settings are restricted to specific private cloud environments. Specifically, these settings are currently allowed only where Advanced Virtualization Settings are supported:

  • Nested Hardware Virtualization set to True
  • CPU Latency Sensitivity set to High
  • Numa Autosize set to True
  • Enable Host Info to VM Tools set to True

Users can identify whether Advanced Virtualization Settings are supported in a given location (or Cluster in multi-cluster locations) as described in How do I Identify Hardware Specifications and Capabilities Available in a Data Center Location

These restrictions mean:

  1. If an Image has any of the settings listed above, the system will not allow Server Deployment from the Image unless the Location (and Cluster in multi-cluster locations) supports Advanced Virtualization Settings.
  2. Users cannot adjust the settings of a Cloud Server to any of the settings above unless the Server's Location (and Cluster in multi-cluster locations) supports Advanced Virtualization Settings
  3. If a Cloud Server Snapshot has any of the settings listed above, users cannot create a Snapshot Preview server unless the Server's Location (and Cluster in multi-cluster locations) supports Advanced Virtualization Settings
    1. Similarly, if the Cloud Server has any of the settings above, the system will not allow Snapshot replication to be enabled unless the replicated Location can support the Advanced Virtualization Settings
  4. In multi-cluster locations, if a Cloud Server Snapshot has any of the settings listed above, it cannot be moved to a cluster that doesn't support Advanced Virtualization Settings


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