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Alistar
Expert
Expert

As I have described above, the VMkernel needs some part of memory to be solely for its own use in order to perform. Below is a table taken from our live environment (if you put it in a graph, it is almost a logarithmic curve):

GB RAMReserved MB
242378
482682
963467
1925129
5129985

This memory value is always provided to the host and never swapped out and would make around 2,5 GB for your 32GB setup. This is why VM performance suffers because their ram gets swapped out to disk, never VMkernel which stays in memory at all times. The active memory is being "touched" and needs to physically fit in with the rest of what is happening under the hood. You should be looking at "consumed" value as this represents all memory pages in RAM.There is some space for overcommitment in ESXi, but it all depends on use cases (it is best used for many identical machines).

Therefore: 29G consumed + 2.5G overhead +1G free ~ 32G physical memory.

Try to read up some more on resource management inside ESXi if you wish to understand this issue deeper: http://www.vmware.com/files/pdf/mem_mgmt_perf_vsphere5.pdf

Stop by my blog if you'd like :slightly_smiling_face: I dabble in vSphere troubleshooting, PowerCLI scripting and NetApp storage - and I share my journeys at http://vmxp.wordpress.com/
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