The new vSpere Resource Guide says this about memory reservations:
"After a virtual machine has accessed its full reservation, it is allowed to retain that amount of memory and this memory is not reclaimed, even if the virtual machine becomes idle. For example, some guest operating systems (for example, Linux) might not access all of the configured memory immediately after booting. Until the virtual machines accesses its full reservation, VMkernel can allocate any unused portion of its reservation to other virtual machines. However, after the guest's workload increases and it consumes its full reservation, it is allowed to keep this memory."
while the Resource Guide for VI3 says:
"The reservation is expressed in concrete units (megahertz or megabytes). When resources are not used, the ESX Server host makes them available to other virtual machines."
It's a different wording , all right, but it gives the impression that reserved and used memory actually is reclaimed in ESX3. Does anyone know what the deal is with this. Has anything changed or does reserved and used memory stay with the VM, unreclaimed, even tho active memory for the VM is less then the reservation even in ESX3?
I believe vSphere continues what was done in VI-3 - when a VM uses its reservation it retains it until it is turned off -
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