Hello,
If an ESXi server fails, the VMs hosted on it will go down or at least become unreachable but VMware HA responds by restarting the VMs on other hosts in the cluster that survived the failure.
My question is when only a single VM fails instead of whole ESXi server then how HA is going to handle.
Regards,
CEH
HA offers both, host monitoring as well as VM monitoring. Host monitoring kicks in in case of a host failure where all VMs have to be restated. VM monitoring works on a per VM basis, where VMware Tools heartbeats as well as I/O is monitored.
André
Under HA if vm crashes then it will reset on the same esxi or on another clustered esxi.
Afaik HA will simply restart the VM, but not necessarily on another host. Whether the VM will run on the same host or another one depends on DRS, i.e. the Initial Placement.
André
Its clear now thank you.
HA not only perform failovers of VM in case of Esxi failure but also provides recovery from failure for a single virtual machine. There is an option of choosing "VM Monitoring" while configuring HA which will monitors the hearbeat of the VM and if after specified period if no heartbeats are detected HA is going to restart the VM either on same Esxi or on different Esxi.
Thanks alex for in detail explanation.
you are welcome dude.
Something I stil can't figure out is the optional HA setting : "Host Monitoring".
What if you ENABLE HA, but you DISABLE 'host monitoring" ?
How will HA be able to detect which host doesn't have a heartbeat?
What could be the reason for enabling only HA, but not 'host monitoring'?
Thanks,
Kris
If Enable Host Monitoring is selected, each host in the cluster is checked to ensure it is running. If a host failure occurs, virtual machines are restarted on another host. Host Monitoring is also required for the vSphere Fault Tolerance recovery process to work properly.
After you create a cluster, enable Host Monitoring so that VMware HA can monitor heartbeats sent by the VMware HA agent on each host in the cluster.
If you need to perform network maintenance that might trigger host isolation responses, VMware recommends that you first suspend VMware HA by disabling Host Monitoring. After the maintenance is complete, reenable Host Monitoring.
The Host Monitoring Status section is new to vSphere and is used to enable the exchange of heartbeats among hosts in the cluster. In VI3, hosts always exchanged heartbeats if HA was enabled, and if any network or host maintenance was being performed, HA could be triggered unnecessarily. The Enable Host Monitoring setting allows you to turn this on or off when needed. For HA to work, Host Monitoring must be enabled. If you are doing maintenance, you can temporarily disable it.
Refer:vSphere Documentation Center
http://searchitchannel.techtarget.com/feature/Enabling-VMware-HA-DRS-Advanced-vSphere-features
As per me, if HA monitoring is disabled & when VM monitoring is enabled, if GuesOS is not working, VM should be restarted on the same host. However, I will confirm this and come back here.
![]()
Yeah, I know all that, but I'm wondering what will happen if you
a) ENABLE HA
b) BUT, at the same time, DISABLE Host Monitoring (Host Monitoring is an optional setting within the HA settings)
?
You would disable HA Host Monitoring when you are performing network maintenance and don't want HA to restart VMs due to the network issue. Disabling Host Monitoring is basically disabling HA.
This is given as an option (vs disabling/turning off HA) so that HA doesn't have to be completely reconfigured whenever you perform maintenance. For more details about this see here: Re: when to disable HA? /cc @hashmibilal
Does this answer your question?
