Question : Configure two ESXi servers for fail over

I have two ESXi servers running about 3-4 VM's each.  I would like to keep the VM's from each host on the other host in the even a host was to fail.  It appears that VMWare has this feature but I would need to upgrade to VSphere and purchase the data backup software from them...sounds expensive.  

Please explain how I go about having a live backup of the VM's on the other server, thanks!

Answer : Configure two ESXi servers for fail over

you could look at this from Veeam - http://www.veeam.com/vmware-esx-backup.html

or, you could see if you can't schedule a snapshot to take place, automatically copy the vmdk file to your second server and commit the snapshot