vCenter High Availability Options | vCenter HA & vSphere HA
For large organizations and enterprises, business continuity is of great importance. If you want to ensure high availability of your vSphere environment including vCenter Server, VMware provides several vCenter High Availability options for you.
vCenter High Availability options
High Availability (HA) refers to the ability of a system to operate continuously without failure for a specified period of time. Today many organizations, especially enterprises, require high availability to maximize business continuity and reduce losses.
Thus, VMware vCenter Server also supports many high availability options.
Released in 2016, vSphere 6.5 makes the vCenter Server Appliance the fundamental building block of a vSphere environment. Along with it was the vCenter High Availability (VCHA), a new feature that applies for vCenter Server Appliance (VCSA) only, provides more availability for this mission-critical service inside the virtualization infrastructure.
What is vCenter High Availability
VMware vCenter High Availability (VCHA) protects not only against host and hardware failures, but also against vCenter Server application failures.
A vCenter HA cluster consists of 3 vCenter Server instances:
- Active node: primary vCenter Server Appliance instance.
- Passive node: secondary vCenter instance to take over the role of active node automatically if it fails.
- Witness node: provides a quorum to protect against a split-brain situation.
The vCenter HA network connects the Active, Passive, and Witness nodes, replicates the server state, and monitors heartbeats. The Active node continuously replicates data to the Passive node.
Using automated failover from active to passive, vCenter HA supports high availability with minimal downtime.
What is vSphere High Availability
vSphere High Availability (vSphere HA) was first introduced by VMware in Virtual Infrastructure 3 in 2006, and has been continuously supported and developed. It is a cluster-level feature that provide protection against the failure of ESXi hosts to increase the total availability of VMs inside the cluster.
vSphere HA pools the hosts and virtual machines into a cluster, and runs a Fault Domain Manager agent on each host within the cluster to monitor them. In the event of a failure, the virtual machines on a failed host are restarted on alternate hosts.
Differing from vCenter HA, vSphere HA requires less network configuration, and is more suitable for situations where consecutive failures are possible. Because vSphere HA will migrate VMs more and more to another available ESXi host, but the vCenter HA cluster is not available and functional anymore after the second failure.
Extended reading: error “insufficient resources to satisfy vSphere HA”
A vSphere HA cluster contains at least 2 hosts, 1 primary host and others are secondary hosts.
- The primary host is mainly responsible for monitoring the status of secondary hosts and coordinating the restarts of protected virtual machines.
- And the secondary hosts mainly contribute to the cluster by running virtual machines locally, monitoring their runtime states, and reporting state updates to the primary host.
Therefore, if you have a vSphere HA cluster with 2 hosts, and have one of them in maintenance mode, that leaves you only 1 single host in the cluster, then you may receive the error displaying “insufficient resource to satisfy configured failover level for vSphere HA”.
In fact, this error does not just in this situation. It is a common issue that indicates the vSphere HA Cluster does not have enough resources to continue restart and run all the virtual machines in the case of a failover.
There are many factors that may cause the error insufficient resources to satisfy vSphere HA:
- Resources such as free memory and CPU are not enough for vSphere HA failover.
- The Manually modified the configured cluster resources percentage option for Admission Control.
- Hostname resolution not working and vSphere HA fail to communicate with cluster nodes.
You can troubleshoot this insufficient vSphere HA failover resources error based factors such as above. If have enough resources but still get the insufficient resources to satisfy vSphere HA error, it is recommended to try disabling Admission Control to resolve this issue.
Looking for a more affordable VM protection measure?
vCenter High Availability is an advanced feature that does not concluded in vCenter Essentials and Foundation. Upgrading your license can significantly increase your VM data protection cost. It may not be cost-effective just for this one feature.
If you are looking for an affordable VM protection measure, you can try AOMEI Cyber Backup, an agentless VMware backup software that supports both paid and free versions of ESXi 6.5-8.0.
A system is not 100% available, but fails occasionally. For organizations and enterprises, a system of high availability basically means high business continuity and high profitability. Therefore, there are many high availability options along with products. This article briefly introduces 2 vCenter High Availability options, vSphere High Availability and vCenter High Availability.
vSphere also provide Fault Tolerance (FT) and Redundancy for you to build a 24/7 IT infrastructure and disaster recovery plan. Check more details in High Availability vs Fault Tolerance vs Redundancy.