Category Archives: FAQ

Notes from High Availability Guide

What happens when host is joined to HA cluster?

Agent is uploaded to the host and configured to communicate with other agents in the cluster. Each host in the cluster functions as master host or slave host.

When does election/re-election of master hosts takes place?

When HA agents are enabled on all hosts, all active hosts (those not in standby, maintenance mode or disconnected state) participate in electing master host.

While re-election happens when master host fails, is shutdown or is removed from the cluster.


Note:

There is only one master host in a cluster and all other hosts are slave. The host which has maximum number of datastores mounted has an advantage in the election.


list down Checklists for HA?

ü All hosts must be licensed for HA. (All editions Standard, Enterprise and Enterprise plus supports HA)

ü Minimum two hosts are needed

ü All hosts need to be configured with static IP address or ensure DHCP is able to provide same address every time.

ü All hosts must have same virtual machine network and datastores

ü All Virtual machines must be located on shared datastores otherwise they cannot be failed over in the case of a host failover

ü For VM monitoring to work, VMware tools must be installed.

ü Host certificate check must be enabled

ü For datastore heartbeat minimum two datastores are needed

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ü vSphere HA supports both IPV4 and IPV6. A cluster that mixes the use of both of these protocol versions, however is likely to face a network partition

Which setting is not available when you configure cluster without hosts?

The Specify a Failover Host admission control policy is unavailable until there is a host that can be designated as the failover host

Which settings are disabled when you move the host to HA cluster?

The Virtual Machine Startup and Shutdown (automatic startup) feature is disabled for all virtual machines residing on hosts that are in (or moved into) a vSphere HA cluster. Automatic startup is not supported when used with vSphere HA.

What is the importance of Host monitoring status?

Host monitoring status enables HA to monitor HA agent heartbeats. Heartbeats are sent by the vSphere agent on each host in the cluster

How to suspend HA?

You can suspend HA by de-selecting Host monitoring

Which setting is not available when you configure cluster without.

The Specify a Failover Host admission control policy is unavailable until there is a host that can be designated as the failover host

Which settings are disabled when you move the host to HA cluster?

The Virtual Machine Startup and Shutdown (automatic startup) feature is disabled for all virtual machines residing on hosts that are in (or moved into) a vSphere HA cluster.

Automatic startup is not supported when used with vSphere HA.

What is the importance of Host monitoring status?

Host monitoring status enables HA to monitor HA agent heatbeats.Heartbeats are sent by the HA agent on each host in the cluster.

If host isolation response is not working what could be wrong?

Check if Host monitoring status is enabled. Host isolation responses require that Host Monitoring Status is enabled. If Host Monitoring Status is disabled, host isolation responses are also suspended. A host determines that it is isolated when it is unable to communicate with the agents running on the other hosts and it is unable to ping its isolation addresses. When this occurs, the host executes its isolation response.

The responses are:

Leave powered on (the default), Power off, and Shut down. You can customize this property for individual virtual machines.

What is dependency of isolation response with vmware tools?

This dependency is specifically on shutdown isolation response. To use the Shut down VM(graceful shutdown) , you must install VMware Tools in the guest operating system of the virtual machine. Virtual machines that are in the process of shutting down will take longer to fail over while the shutdown completes.

Virtual Machines that have not shut down in 300 seconds, or the time specified in the advanced attribute das.isolationshutdowntimeout seconds, are powered off.

What is the drawbag of disabled isolation response?

Disabled isolation response may lead to split brain situation when host loses both management and storage network connectivity. In this case, the isolated host loses the disk locks and the virtual machines are failed over to another host even though the original instances of the virtual machines remain running on the isolated host. When the host comes out of isolation, there will be two copies of the virtual machines, although the copy on the originally isolated host does not have access to the vmdk files and data corruption is prevented. In the vSphere Client, the virtual machines appear to be flipping back and forth between the two hosts. To recover from this situation, ESXi generates a question on the virtual machine that has lost the disk locks for when the host comes out of isolation and realizes that it cannot reacquire the disk locks. vSphere HA automatically answers this question and this allows the virtual machine instance that has lost the disk locks to power off.