Virtual Machine RAM high utilize
High memory utilization – the problem may occur when VM is “vMotioned” between ESX3.5 (old cluster – HW configuration Dell PE2950 2xQuadCore L5410 32GB RAM, ESX3.5 U5) and vSphere4 (new cluster – HW configuration Dell R710 2xQC E5504, 40GB RAM, ESX4 U1 with all patches). What does it mean ? VM i.e. with 1vCPu and 2GB RAM when is hosted by ESX3.5 an average RAM usage is about 50% with picks up to 75%, just after vMotion to vSphere4 RAM usage grow to 100% (picture below).
This BUG is know and solve by VMware, detailed description is KB1014019 . There is a small workaround to solve this issue, set Mem.AllocGuestLargePage parameter to 0 (zero).
A few second after set above parameter memory utilization get back to normal state like it was on old infrastructure.