Will HA and DRS work if Vcenter is down?

[beckham007fifa]

Hi Guys,

I just wanted to know whether HA or DRS will work if my vcenter goes down for some reason. If yes how does it have the cluster information with itself for restarting the machine and to adjust the loads.

Thanks,

[peetz · Accepted solution]

Hello,

HA will work, because there is an HA agent running on each host, and the hosts monitor each other and keep lists of running VMs that need to be restarted in case of a host failure. vCenter is just used to (de-)activate and configure HA.

DRS will NOTwork without vCenter, because vMotion recommendations are computed by the vCenter service, and it also initiates the migration processes.

- Andreas

[beckham007fifa]

Yeah, i too have read the same but suppose you have a cluster created with 10 hosts and your vcenter is down and never came up, how long the HA will continue to work and will the host be knowing their group of hosts which formed the cluster. Suppose if I have 5 clusters with 10 hosts, HA agent installed on all of them in that case how will the host will be recognizing their scope? and for which all host they have to act/react and how long this HA will continue to work if vcenter never comes up. This is bugging me since yst when vcenter goes down and one of the ESX host failed to go to maintenance mode when I planned for patching it. Thanks.

[peetz]

The HA agent on each host keeps a list of all the other hosts in its cluster and periodically tries to reach them.

It works completely independent from the vCenter service, so HA continues to function even if the vCenter server is down for a very long time.

For detailed information on how HA works (in releases prior to vSphere 5) read this white paper.

With vSphere 5 HA was completely rewritten, but this basic functionality is still the same. See the Online Docs here.

- Andreas