Hi...
We have a project going on where Cisco requires a 1:1 vCPU to core mapping on any particular host for their UC virtual machines. When we add the 3 VMs that will be on this host, we get an alert saying:
Unable to apply DRS resource settings on host. The available CPU resources in the parent resource pool are insufficent for the operation. This can significantly reduce the effectiveness of DRS.
The first VM has 6 vCPUs, the second and third each have 4 vCPU's for a total of 14 vCPUs. Cisco design docs say that ESXi reserves approximately 1 core for itself and to take that into account. Technically this should leave us with 1 spare core. We have 4 hosts, each host has 16 cores, 2.7 GHz processors. We are running ESXi 5.5 Update 1 and vCenter 5.5 Update 1b. HA is set to spare host with host #4 being the spare.
In order to ensure the 1:1 mapping, we are setting the CPU reservation on each VM to a multiple of the # of vCPUs (For example, 2699MHz x 6 vCPU = 16194MHz.
Any idea why we might be getting this error if technically there should be at least 1 core free? I have a case open w/ Cisco and they have one open with VMware but I'm curious to see what other people think.