ESXi

i had 1 cluser confirgured HA  and added physical host ,my question is if any esx host goes down ,the vm will migrate to another esx host with down time , what is the backend process going , what is hagent , how it will work, 

ieg: if any esx server goes ,how will the vm  moves to another esx server, what is technology in the backend process?

Take a look at http://www.yellow-bricks.com/vmware-high-availability-deepdiv/ This explains HA very well.

André

I do not believe Duncan's post states what the underlying technology is. VMware HA is based on  technology developed by Legato called Automated Availability Manager (AAM). Duncan's post does a really good job explaining how the technology works and what you should take into account when designing HA clusters.

You can also see: http://communities.vmware.com/thread/44823

Try this pdf.

http://www.vmware.com/pdf/vmware_ha_wp.pdf