Cluster HA depends on shared storage and dynamic migration technologies to provide simple and efficient HA services for applications running on all VMs in the cluster. It reduces service interruption caused by host hardware failure. Cluster HA is applicable to scenarios that require service continuity.
UIS Manager virtualizes a group of hosts into a cluster that uses a shared resource pool. After you enable HA for the cluster, UIS Manager monitors running state of all hosts and VMs in the cluster.
When a host fails, UIS Manager migrates the VMs on the host to available hosts in the cluster.
When a VM fails, UIS Manager restarts the VM. If the VM is restarted, UIS Manager does not migrate the VM. If the restart fails, UIS Manager migrates the VM to another host and restarts it.
When the network between a host and the shared storage fails, UIS Manager migrates the VMs on the host to available hosts in the cluster.
Automatically monitors running state of hosts and VMs and migrates a failed VM or VMs on a failed host to other hosts in the cluster.
Reserves enough resources for VMs to restart if hosts fail.
Automatically migrates VMs between hosts to ensure service continuity in case of hardware failure.
Automatically selects suitable hosts for VMs on a failed host based on the resource usage if you enable both HA and DRS for the cluster.
Before you enable HA for a cluster, make sure all hosts in the cluster have reserved sufficient system resources so that the VMs can migrate between the hosts.
When you enable HA for a cluster, make sure the following requirements are met:
All hosts in an HA-enabled cluster must have the same vSwitch configuration, including the number of vSwitches, name, and forwarding mode.
In an HA-enabled cluster, all hosts must use CPUs from the same manufacturer. Clusters containing hosts that use CPUs of the same model from the same manufacturer can provide better migration compatibility.
To ensure that VMs in an HA-enabled cluster can migrate between hosts in the cluster, make sure the image files of all VMs in the cluster are saved in the shared storage. As a best practice, do not enable HA or DRS if the VMs must use the local storage.
During the process of enabling or disabling HA for a cluster, do not start, deploy, or migrate VMs or restart or shut down hosts in the cluster.
To prevent VM name conflict, make sure no hosts in abnormal state exist in a cluster before you disable HA for the cluster. If VM name conflict occurs, enable HA for the cluster again.
To avoid cluster HA and VM failures, do not edit the cluster HA settings during VM migration if DRS and DPM are enabled. Before disabling cluster HA, disable DRS and DPM and make sure no VM is being migrated.
On the top navigation bar, click Hosts, and then select Cluster Management > Cluster Configuration from the navigation pane.
Click HA.
Configure the HA parameters as described in "Parameters."
Click Save.
Enable HA: Set the HA state.
Boot Priority: Select a default boot priority for the VMs in the cluster. Options include Low, Medium, and High. You can set the boot priority for a VM when you add or edit the VM. After a host fails, the system migrates the VMs on the host based on their boot priorities until all the VMs are migrated or the cluster does not have any available resources.
Service Network HA: Configure whether to enable service network HA. When the service network of a VM fails, the VM can be migrated to another host. VSwitches that are not bound to physical NICs and those that use the management network do not support HA failure detection.
HA Access Control: Select whether to enable HA access control. If you enable HA access control, configure one of the following parameters:
Min. Nodes for HA: Specify the minimum number of hosts for HA to take effect on the cluster. If the number of hosts that are operating correctly in the cluster is smaller than the specified minimum node number, HA cannot take effect on the cluster.
Failover Hosts: Select hosts used for migration of failed VMs. These hosts cannot be used for common VM migration or VM adding operation. The failover hosts must use the same shared storage as the service hosts and cannot contain running VMs.
Resource Reservation: Set the reserved CPU and memory percentages. When the remaining resources in the cluster are less than the specified percentage of resources, you cannot start new VMs, set the VMs to running or suspending state, or migrate running VMs to the cluster.