How To Create Data Center and Cluster in oVirt / RHEV

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Data center in oVirt / RHEV?

A Data center is the top-level organizational object in oVirt / Red Hat Virtualization platform. It can be described as a self-contained virtualization environment. Data center contains all the physical and logical resources – clustershosts, storage domains and logical networks.

All clusters and hosts in a data center share the same storage – this makes data center fit for isolating resources that belong to an organization or group from other organizations or groups that normally would not have access to those resources. A single Administration Portal is used to administer multiple data centers in the virtualization infrastructure.

A single data center in oVirt / RHEV virtualization may consist of:

  • Resources located in a particular physical data center at a particular location/region.
  • Systems and storage that belongs to a particular business unit of an organization.
  • Multiple clusters which can contain multiple hosts
  • Multiple storage domains
  • Multiple virtual machines on each of the hosts in the cluster(s)

When you install oVirt/RHEV virtualization, a data center named Default is created automatically. You can always create additional data centers from the Administration Portal as admin user. Here is a picture showing all the components in a single data center.

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An overview of multiple data centers with Management components.

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Clusters in oVirt / RHEV?

Now that we have defined what a data center is, let’s switch the gear towards Clusters in Red Hat Virtualization Platform. A cluster is defined as a logical grouping of hosts, in a single data center, with the same type of CPU architecture and model, as well as storage domains. All hosts in a cluster must be configured with the same resources – storage domainslogical networks, and have sufficient computing capacity for live migration of Virtual Machines to be possible. The virtual machines can only live-migrate to other hosts defined within that same cluster.

If the compute hosts in a cluster have a mix of CPU models, they use only the features present in all models (this is determined by the oldest physical CPU family in the cluster). The cluster is the highest level at which power and load-sharing policies can be defined. Gluster Storage Servers are run within at the cluster level. During installation, oVirt will create a default cluster in the default data center.

Creating a Data Center in oVirt / RHEV

In this section we shall cover the procedure of creating a new data center from Administration Portal when logged in as admin user. We’ll just create a data center without any associated resources as this is covered in subsequent fragments.

To create a new data center, click the Compute, then Data Centers tab.

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This will display all the options available for managing data centers.

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To create a new data center, click New.

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You’re required to fill the following information:

  • Name: This is the name you want to use for the data center
  • Description: Inout more details about the data center
  • Storage TypeWhere you select the storage type to use in the new data center. Available options are (Shared & Local). Shared storage type allows for multiple clusters and hosts to be contained in a data center for running virtual machines. If you choose Local, created data center will be restricted to a single cluster with only one host. For local, storage in the data center can be provided by the host’s local file system.
  • Compatibility Version: Choosing Red Hat Virtualization Compatibility Version that is supported by the data center. It is recommended to go with the latest available version.
  • Quota Mode: Quotas are used to Memory, CPU, and storage resources. For this you have three available options.
    • Disabled – This will turn off quota-based restrictions in the data center
    • Audit – With this setting, quota limits will be enabled but not enforced.
    • Enforced – Uses set quota settings to restrict resource usage

This is a sample data center creation screenshot with populated details.

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Once you click OK button. A new pop-up window – “Data Center – Guide Me” is displayed.

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The wizard gives you an easy way to configure other resources that should be created before data center is useful. Click the “Configure Later” button if you wish to complete other data center configurations later.

The new data center we just created have status as “Uninitialized“. This will change to “Up” after we assign resources and confirmed to be usable.

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The data center we created have no cluster at the moment.

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Creating a Cluster in oVirt / RHEV

Before we create a cluster in oVirt/RHEV environment, we need to prepare storage and compute servers that will be used as hosts in the platform. Check out the guides in the links below for how to steps.

Validate if all hosts have the same CPU type, or determine the oldest CPU family in use. This can be done by clicking on Compute > Hosts > Host-name General > Hardware. See below example;

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Navigate to Compute > Clusters > New

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Details to fill in required fields include;

  • General Settings
    • Data Center: Select the data center to which this cluster belongs
    • Name: A useful cluster name
    • Management Network: A logical network to be assigned to all hosts that will be in this cluster. Can be changed to another logical network later.
    • CPU Architecture: Collected from your host information
    • CPU Type: Collected from your host information
    • Compatibility Version: It specifies the common API protocol version supported among all hosts and management engines that will communicate together as a single oVirt Virtualization infrastructure
    • Switch Type: You can configure only one at time. Default is Linux Bridge.
    • Enable Virt Service – If checked it allows hosts in this cluster to run virtual machines.
    • Enable Gluster Service – Valid for hosts used to run Red Hat Gluster Storage service, and not for running virtual machines
  • And more

Explore other site-specific configuration options under:

  • Optimization – Configure memory page sharing threshold, CPU thread handling, and memory ballooning.
  • Migration Policy – Rules to determine automatic migration of existing VMs between hosts
  • Scheduling Policy – Rules to determine on which host to new virtual machine will start.
  • Console – Setting console connection protocols and proxies, such as SPICE.
  • Fencing Policy – Actions taken when managed hosts fail, to ensure that attached storage is not corrupted.
  • MAC Address Pool – Defining the MAC address range to be used for NICs on VMs in this cluster, other than using the data center default pool

See my configuration fields below:

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You now have a data center and cluster added to your oVirt based Virtualization platform. Next you add hosts, storage, and network resources and start using it.

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