1. vSphere HA组件
2. vSphere Cluster
A vSphere cluster is a configuration of more than one VMware ESXi server aggregated together as a pool of resources contributed to the vSphere cluster. Resources such as CPU compute, memory, and in the case of software-defined storage like vSAN, storage, are contributed by each ESXi host.
2.1 HA
VMware vSphere HA is cost-effective and allows automated restarts of VMs and vSphere hosts when there is a server outage or an operating system failure detected in the vSphere environment
2.1.1 Master and Subordinate Hosts
When you enable vSphere HA on a cluster, a particular host in the vSphere Cluster is designated as the master of vSphere HA. The remaining ESXi hosts in the vSphere Cluster are configured as subordinates in the vSphere HA configuration
When vSphere HA is enabled for a cluster, all active hosts (no maintenance mode, etc) participate in electing the master host. If the elected master host fails, a new election takes place where a new master HA host is elected to fulfill that role.
2.1.1.1 master host
1 Monitors the state of the slave subordinate hosts – If the subordinate host fails or is unreachable, the master host identifies which VMs need to be restarted
2 Monitor the power state of all VMs that are protected. If a VM fails, the master vSphere HA node ensures the VM is restarted. The vSphere HA master decides where the VM restart takes place (which ESXi host).
3 Keeps track of all the cluster hosts and VMs that are protected by vSphere HA
4 Is designated as the mediator between the vSphere Cluster and vCenter Server. The HA master reports the cluster health to vCenter and provides the management interface to the cluster for vCenter Server
5 Can run VMs themselves and monitor the status of VMs
6 Stores protected VMs in cluster datastore
2.1.1.2 subordinate host
1 Run virtual machines locally
2 Monitor the runtime states of the VMs in the vSphere Cluster
3 Report state updates to the vSphere HA master
2.1.2 Failure Types
There are three types of failures that can happen to trigger a vSphere HA failover event.
2.1.2.1. Failure
A host has stopped working in some form or fashion due to hardware or other issues.
2.1.2.2 Isolation
a network event that isolates a particular host from the other hosts in the vSphere HA cluster
2.1.2.3 Partition
a subordinate host losing network connectivity to the master host of the vSphere HA cluster
2.2. DRS
2.2.1 fully automated
DRS applies both the initial placement and load balancing recommendations automatically
2.2.2 Partially Automated
With partial automation, DRS applies recommendations only for initial placement of VMs. for load balancing, give recommendations to admin, not load balancing automatically.
2.2.3 Manual
you must apply the recommendations for both initial placement and load balancing recommendations
2.2.4 Migration Thresholds
control the amount of imbalance that will be tolerated before DRS recommendations will be made
The range is 1 (most conservative) to 5 (most aggressive).
With more aggressive settings, DRS tolerates less imbalance in a cluster. The more conservative, the more DRS tolerates imbalance.
2.2.5 VM/Host Rules
control the placement of VMs in your vSphere DRS-enabled clusters. The VM/Host Rules allow you to run specific VMs on specific ESXi host. You can think of this as affinity rules in a way.
The VM/Host rules allow you to:
Keep virtual machines together
Separate virtual machines
Tie Virtual Machines to specific hosts
Tie Virtual Machines to virtual machines
2.2.6 VM Overrides
VM Overrides to override global settings set at the cluster level for HA and DRS to define more specific settings for each individual VM.
