We using vSphere 5 to host over a dozen virtual servers and all are Windows 2008 R2 or newer.
I'm experiencing a bad delay of a few seconds after a VM has been idle for a little while (may only be a few minutes). If I ping one of the virtual machines I get one response followed by time outs, after this it seems consistent until I leave the machine alone again.
I thought at first that the ESXi servers might just be running out of resources but they only ever really sit on a few hundred mhz and there's always at least 5-10 GB of RAM free. I've also tried setting reservations in the VM settings but that didn't seem to help either. Power saving settings for vSphere are set to balanced.
Services other than ICMP are also impacted by this delay.
Thanks in advance for your help.
Turned out there was a configuration error by the third party that installed the infrastructure for ESXi and we had a loop going on. Hence the dropping packets and poor performance. Thanks to everyone that provided suggestions.