As you know one of the most important component in VMware Vsphere is HA(High Availability).
But if you want to run HA in your Datacenter, before it you must know some tips about HA, how to implement and how to configure it, in this article we wont describe how to implement HA in your cluster or how to add a host step by step, but in this article we want to say something important than "How to implement HA Component!" and you must know it before every change in your activated HA Datacenter.
First tip is about VSAN(Virtual SAN), as you know this is Vmware solution for Shared storage, and its one of an amazing features in Vmware Vsphere , but you must know some tips about it when you want run this service or component in your datacenter with HA , for example if you have a Cluster without VSAN feature, HA transfer its all data by Management Vmkernel NIC and when you enable VSAN in the cluster, HA redirect its own traffic via which vmkernel have VSAN enabled.
Another tips about VSAN and HA is, you can not enable VSAN when HA is Active, you must disable HA then enable VSAN and then re-enable HA.
Next tip is about NIC Configuration when you have VSAN and HA as a active component in your cluster, as before we say about HA traffic transfer method in the clusters with VSAN enable state, you know HA send and receive its traffic via VSAN enable NIC, but once of the important tip about this condition is "you can not edit your NIC setting as a usual " ! you can change anything of your VSAN NIC setting, but its not work properly, cause HA Agent not configured(and its not suited for such situations) to pick up new setting from VSAN NIC you newly configure it. After VSAN enabled in your cluster you must perform this step for any little change in your NIC settings:
1- Disable Host Monitoring for your cluster
2- Mack VSAN Network NIC change
3- Right click on each host in your cluster and select Reconfigure for Vsphere HA
4- Re-Enable Vsphere HA Monitoring
Next tip is about IP v6, if you want use IPv6 in your Datacenter you must know every host in your Cluster must have IPv6, you can not have a cluster with 2 host with IPv6 and 5 Host with IPv4.
Another tip about IPv6 is if you use IPv6 for your HA network, you can not set IPv4 as a Isolation Address.
To upgrade your Datacenter from IPv4 to IPv6 you must before any change in IP Address configuration, set your HA into disable state and after changes, re-enable HA.
