Distribution of virtual machines between cluster nodes

From ISPWiki
Jump to: navigation, search
Hierarchy: VMmanager KVM -> Cluster configuration
VMmanager Cloud -> Cluster configuration

A cluster node virtual machines will be created on, is selected when you add a virtual machine. You can select a cluster node from a list of the existing ones or it can be selected automatically (default).

Automatic selection of a cluster node

  1. VMmanager generates a list of cluster nodes. The list is sorted out based on the number of virtual machines created on the cluster;
  2. The system checks:
    1. its status;
    2. the maximum number of virtual machines created on the node;
    3. error notifications on the cluster node;
    4. VM location rules;
    5. available resources and overselling;
  3. A new virtual machine will be crated on the first node that meets all the requirements. If no cluster nodes meet the requirements, the virtual machine won't be created.

Cluster node status

There are 2 statuses: "Blocked" and "Unblocked". Virtual machines can be created on a cluster node depending on status. A blocked cluster node will be excluded from the list.

You can block a node in the the "Cluster settings" section -> "Cluster nodes". Alternatively, you can add the CreateVmDisableNodeTimer parameter into the VMmanager configuration file. This parameter specifies period in minutes when a cluster node will be excluded from the list of nodes where virtual machines can be created automatically. After you add the parameter, the cluster node will be blocked for a specified period after a virtual machine is created. If the virtual machine is installed before that period, the node will get unblocked.

Maximum number of virtual machines

When creating a cluster node, you can specify the "maximum number of VM" (unlimited by default), which defines the number of machines that can run simultaneously on a cluster node. The check will be passed successfully if the maximum number is not reached.

Error notifications

The check will be passed successfully, if the cluster node is up and running.

VM location rules

Location rules allows to control how virtual machines are spread among cluster nodes.

Navigate to "Cluster settings" -> "Location rules".

«Location rules»
  • Priority - execution order. The rule with the smallest value will be executed first.приоритета;
  • Rule type - it can be the name of virtual machine or OS template;
  • Value - value for comparison;
  • Operand- Contains - checks that the "value" field is included into the property: Does not contain - checks that the "Value" field is not included into the property;
  • Cluster node - defines the cluster node that the rule will be applied to. It can be a single node or all cluster nodes;
  • Action - a rule allows to add or delete a node, do not perform any actions. Add - the node that meets the requirements will be added to the list of cluster nodes where virtual machines can be created. Delete - the cluster node that meets the requirements, cannot be used for adding new virtual machines. Do not perform any actions - proceed to the next step.
  • Stop processing - with this option selected the next rule won't be processed.

Available resources and overselling

The system will check available resources on a cluster node taking into account the amount of overselling. The check will be passed successfully if there is sufficient resources for creating a new virtual machine.