1. Suppose we have only two esxi host on cluster, are we able to configure FT on VM, if yes then when if host fails, then what will happen,then where will be next secondary(Shadow) VM will be created.??.
Hope the below explanation clears everything for you:
VMware vSphere Fault Tolerance (FT) is an awesome feature allowing you to set up a total fault-tolerant zero-data-loss architecture with a single right-click of a mouse. In case the underlying host has a hardware problem, there is zero downtime, zero data loss, zero connection loss, and continuous service.
To put it simply, vSphere FT works by continuously replicating an entire running VM from one physical server to another. The FT-enabled VM has two replicas:
1. Primary VM
2. Secondary VM
Each VM is running on a different ESXi host. The replicas are logically identical; they represent a single VM state and a single network identity, but they are physically distinct.
Each replica has its own virtual machine files, such as configuration files (VMX) and virtual machine disk files (VMDK).
After activation of FT, the first synchronization of the virtual machine disk files (VMDKs) happens using vSphere Storage vMotion. Subsequently, vSphere FT will mirror VMDK writes between the primary and secondary VM over the FT network.
When a physical server fails, VMware HA automatically restores redundancy by restarting a new secondary VM on another host. The VM state, network identity, and all active network connections for the VM will be identical, reflecting the whole state as a primary VM again. If the host running the secondary VM fails, VMware HA starts a new secondary VM on a different host.
There will be no new creation of a secondy VM when one of two hosts in a cluster fails. We have a couple of Dell VRTX with 2 Blades in the Field which protect the VMs with FT.