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).
and you can notice ESX memory host usage rapidly grows up (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.
yeah, exactly. One important thing to add is that ESX host must be rebooted after this change.