We have an environment with only 2 ESXi hosts with a shared storage where one of the VM being hosted is a MS-SQL-08R2.
I understand that the vCenter Server can be installed as a VM and in any case it requires a SQL database (which is planned to be run in an existing VM "MS-SQL-08R2").
If I install vCenter Server as a VM and including the MS-SQL-08R2 VM both being hosted on that only 2 ESXi host and in any case randomly, one of the 2 host (that hosts the vCenter Server VM and/or MS-SQL-08R2" VM) fails. Will HA not able to function and reboot all VMs on another good host?
HA would work even when the vCenter is down. All you have to take care of, is that there is enough room on each server to accommodate VM's running on both servers if one of them go down.
Yes your VM will be restart on the other host. Each host have a list of information regarding ha information. And know which VMs a host need to restart or not.
the vCenter is only needed to configure the HA settings of a cluster. Then a HA-agent is installed on the ESXi hosts.
The HA-process itself is done by the hosts, so even if the host with the vCenter VM crashes, HA will continue to work and reboot the VM on the second host.
If you want to know more about HA functionality I recommand to read Duncan's blog: vSphere High Availability (HA) Technical Deepdive - Yellow Bricks
But I thought one of the main role for HA to function is that the vCentre Server detects the heart beats of the host yea?
Or the HA function in the latest 5.5 no longer requires heart beat? and just as Tim said a HA agent inside the ESXi hosts looks after everything?
Not the vCenter. The slaves send heartbeat to master host. once one of them is down the HA is triggered.
Also, Read the master versus slave and heartbeating section of the link Tim provided.
Thank you guys, then it seems I can use only a minimum of 2 host for a production HA environment.
One more quick question, suppose we have host-a (primary) and host-b (slave), vCenter Server be placed to some other hosts (or even off the site).
host-a will be turned on 24x7 and host-b will be turned off for power saving, will vCenter Server or HA-agent trigger host-b to wake up on LAN should host-a fails?
No, that would not be possible. As i told vCenter is only used for configuration of the HA. The masters and slaves report to each other. When you enable HA and power off the host, the HA will kick in and consider that host is down. Only when you manually restart it it might join back the cluster.
Why not use Distributed power management with HA? That will power off one host if there is less load and then power it on when needed automatically.
Hi, we are very small scale implementation and our licensing package only comes with vMotion, HA, Data Protection, vShield Endpoint, vSphere Replication unfortunately.....
Do you have any recommendations on existing package and hardware availability to reach such goal?