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VMWare, host memory, guests memory and machine memory

kaare_t asked
Hi all,

I've tried to search the internet for a couple of days now trying to figure out how much physical memory I need in my VMware'd server. English is not my primary language and I have some problems understanding all the terms and figures, so I figured I could post a question with my specific config:
1 physical server running VMware vSphere 5.x
2 Viritual servers, server 1 has 4GB RAM and server 2 has 8GB RAM

This means that my guest OS'es has a total of 12GB RAM, and here's my question: How much physical memory should I install in my server? The way I see it there's 3 different options:
1. Install a total of 26GB RAM (((guest os + guest os) x 2) + 2GB extra for the vSphere)
2. Install a total of 14GB RAM (guest os + guest os + 2GB for the vSphere)
3. Install a total of 18GB RAM (biggest guest os x 2 + 2GB extra for the vSphere)
4. ?????

As mentioned I don't get the official VMware documentation, sorry for this. Hope you can give me a clear answer to my specific setup.

Best regards!
Watch Question

VMware and Virtualization Consultant
Expert of the Year 2017
Memory in a VMware vSphere environment *WILL ALWAYS* be the Bottleneck.

We work on the following guide

Total Memory in Host = (4GB for the Hypervisor + Total amount of VMs) * 20%

So if you have Guest OS which need 12GB

Total  = (4GB + 12GB) * 20%

Total = 20GB

You then need to look at your server, to ensure it's balanced, which may mean increasing it slightly to fit DIMM requirements, and Channels, Banks for processors.
Andrew Hancock (VMware vExpert / EE Fellow)VMware and Virtualization Consultant
Expert of the Year 2017

Also if this is the free version of ESXi 5.0, it only supports a total of 32GB.


No, not running free version (I'm running Essentials).

Wish that VMware could write it that simple in their documentation......

Thanks a lot!

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