Statistics form VMware are only statistics they are not true ?

[Paulo3]

Hi,
I am searching a information about the metrics and how 'real' they are.
We are having environment with ~9k servers and planning to buy more Host's.
The case is that we have to estimate it by the real guest utilization so we could do the rightsizing.

I am preparing the metrics especially for the RAM utilization for each VM (get-stat mem.usage.average).
My question is form where or how does this metrics are obtained are they collected from Guest Operating System via VMware Tools or are they esxi top ?
Is there any document (I have not find it yet, sorry) describing how it does work?
I am searching an argument for the statement that all statistics form VMware are only statistics they are not true and the only way is to get them form the guest OS inside VM 

Thank you very much!

[LucD]

I think most of your questions are already answered in your other thread Re: get-stattype/ get-stat missing metrics - VMware Technology Network VMTN
Or at least in the documents that the thread points to.

From which source did you get the statement "all statistics from VMware are only statistics they are not true and the only way is to get them from the guest OS inside VM"?

If you want to have data to plan "rightsizing", your best source would be the data that vSphere sees, not the data from inside the Guest OS imho.

[Paulo3]

OK, so, ymmm that is right...
All of my question can be answered here: https://communities.vmware.com/t5/Storage-Performance/Performance-Monitoring-and-Analysis/ta-p/27720....
And with whitepaper https://www.vmware.com/content/dam/digitalmarketing/vmware/en/pdf/techpaper/vmware-performance-analy...

[LucD]

So your questions are answered?