Chapter 10. Clusters
10.1. Cluster Elements
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.
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.
