FT & HA

[PKKR]

Hi,

I am little bit confused here., what is the diff between HA & FT?

From my understanding:

HA - VMware HA allows the VM's running on ESX hosts to automatically recover from host failures. If HA is enabled, if the host fails., all the vm's associated with it will restart on the next available host.

FT - When one VM fails, it migrates to another ESX host without any downtime and creates one copy in another ESX host.

Will FT work if we have only 2 hosts in a cluster. Can we enable FT and HA both at a time? What is the exact difference?

Thanks,

Prashant

[weinstein5 · Accepted solution]

Think of FT having two VMs that are running one is the primary while the seondis a mirror of the primary recording all the changes that all occuring on the priimary - so if the primary does it will immediately pick up the load with no intteruption - whil HA the VM is down and restrats -

Yes FT can run on a 2 nodes and yes the hosts can be a part of an HA cluster -

[rickardnobel]

Prashant wrote:

From my understanding:

HA - VMware HA allows the VM's running on ESX hosts to automatically recover from host failures. If HA is enabled, if the host fails., all the vm's associated with it will restart on the next available host.

Yes, that is correct. The VMs will be be restarted on the different hosts that has survived. Note that the VMs itself will be "crashed" and then restarted, which might mean that they are internal corrupt.

FT - When one VM fails, it migrates to another ESX host without any downtime and creates one copy in another ESX host.

As noted above there is a primary and secondary VM available at all times, think of it as a "shadow VM", with an exact RAM copy running at another host. This will mean no VM-crash and no data loss even if the host hardware fails.

[PKKR]

Hi Einstein,

If we enable FT for a VM12 on Host1 and also enable HA on Host1. If the host goes down what will happen to VM12., will there be any downtime., will FT work (or) HA works for that particular VM.

[rickardnobel]

Prashant wrote:

If we enable FT for a VM12 on Host1 and also enable HA on Host1.

FT needs HA configured for the whole cluster. HA will protect all VMs by trying to restart them after a host failure and FT could give selected VMs a higher degree of protection.