I have noticed that some Linux based virtual machines become gradually slower until I reboot them. At first I suspected hacking and resource abusing but after several vm rebuilds from the scratch and being extra ultra careful security wise, I have ruled the hacking out. Now I'm suspecting that ESX hosts do not have enough RAM and are swapping it for the less busy VMs.
How could I verify whether this is the case or not?
ESX#1: ESX 3.5 8x3GHz, 32GB RAM. 7 vms ESX#2: ESX 3.5 8x3GHz, 32GB RAM. 25 vms 70GB configured guest RAM in total over all the vms.
ESX1 has occasionally an alert that memory is getting low but it's only 24GB of 32GB.