I’ve never liked the disconnect between power management (DPM) and some of the other features built into vSphere 4. One of the more aggravating situations occurs when a host hosting templates and powered down VM’s goes into standby. When this occurs you lose the ability to deploy servers from your templatized VM’s. The same situation occurs with VM’s that are powered off. They become a hostage on the suspended host.
I’ve come up with a simple workaround. Since templates and powered down VM’s aren’t consuming any host resources you can usually be assured that they are going to stay were you put them. In other words, they aren’t going to drift around as DRS does its job. With this in mind, I’ve excluded one host from participating in DPM while keeping the remainder active. You can do this by:
Right clicking on your cluster -> Edit Settings… -> VMware DRS -> Power Management -> Host Options
Select the host that you want to keep running (that will house your powered off VM’s and templates) and click the “Power Management” column for that host. Select Disable and click OK. If you have DPM configured for automatic, the remaining hosts should still reflect the “Default (Automatic)” setting under the “Power Management column”. The last step is to migrate your powered down VM’s and templates to the DPM disabled host.
With this done, you should now be able to reliably deploy VM’s from templates and continue to allow DPM manage the power status of the remaining hosts.