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Chapter 10. Clusters

10.1. Cluster Elements
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The clusters collection provides information about clusters in a Red Hat Enterprise Virtualization environment. An API user accesses this information through the rel="clusters" link obtained from the entry point URI.
The following table shows specific elements contained in a cluster resource representation.
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Table 10.1. Cluster elements
Element Type Description Properties
name string A user-supplied, human-readable name for the cluster. The name is unique across all cluster resources.
description string A free-form, user-supplied, human-readable description of the cluster.  
link rel="networks" relationship A link to the sub-collection for networks associated with this cluster.  
link rel="permissions" relationship A link to the sub-collection for cluster permissions.  
link rel="glustervolumes" relationship A link to the sub-collection for Red Hat Gluster Storage volumes associated with this cluster.  
link rel="glusterhooks" relationship A link to the sub-collection for Red Hat Gluster Storage volume hooks associated with this cluster.  
link rel="affinitygroups" relationship A link to the sub-collection for virtual machine affinity groups associated with this cluster.  
cpu id= complex A server CPU reference that defines the CPU type all hosts must support in the cluster.
data_center id= GUID A reference to the data center membership of this cluster.
memory_policy complex Defines the cluster's policy on host memory utilization.
scheduling_policy complex Defines the load-balancing or power-saving modes for hosts in the cluster.
version major= minor= complex The compatibility level of the cluster.
supported_versions complex A list of possible version levels for the cluster.
error_handling complex/enumerated Defines virtual machine handling when a host within a cluster becomes non-operational. Requires a single on_error element containing an enumerated type property listed in capabilities.  
virt_service Boolean Defines whether to expose virtualization services for this cluster.  
gluster_service Boolean Defines whether to expose Red Hat Gluster Storage services for this cluster.  
threads_as_cores Boolean Defines whether hosts can run virtual machines with a total number of processor cores greater than the number of cores in the host.  
tunnel_migration Boolean Defines whether virtual machines use a libvirt-to-libvirt tunnel during migration.  
trusted_service Boolean Defines whether an OpenAttestation server is used to verify hosts.  
ballooning_enabled Boolean Defines whether ballooning is enabled for the cluster.  
ksm Boolean Defines whether ksm is enabled for the cluster.  

Note

When a host's free memory drops below 20%, ballooning commands like mom.Controllers.Balloon - INFO Ballooning guest:half1 from 1096400 to 1991580 are logged to /etc/vdsm/mom.conf. /etc/vdsm/mom.conf is the Memory Overcommit Manager log file. An event will also be added to the event log if a virtual machine does not respect a balloon.
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