After an import of 40 ESX 3.5 virtual machines from an external company, we discovered that we couldn’t power up any new virtual machines unless we disabled “Admission Control” on that specific cluster.
After correcting the settings on the cluster it showed on the summary page of the cluster that VMware HA had a Configured Failover capacity of 1 host and the Current Failover Capacity was 0 hosts. And there was a warning stating: “Insufficient resources to satisfy HA failover level on cluster ”
After some research I came accross a nice article that explains how Vsphere calculates the weight of the virtual machines. After checking the settings of each virtual machine we discovered that one of the machines had a reservation on the memory. And one machine had a reservation on the CPU.
After correcting these settings to the defaults the errors disappeared.
So always check imported virtual machines for non-default settings.