Edit: I started this blogpost more than a week ago, but I never finished it. Just as I wanted to complete the blogpost, I found out VMware released a new whitepaper about VMware vSphere Memory management. I’ve added the best practices on the bottom of this blogpost.

This hour and a half session about “Host” and “Guest” memory usage was very interesting. The topics in this session were:

• Define host and guest memory usage and ask some questions
• Memory management concepts
• Answer our questions
• Best practices
• Future Directions

It covered way more than I can put in this blogpost, but I want to highlight some of the things that were discussed during this presentation. The most important part to remember is:

The ESX hypervisor doesn’t have a clue which memory pages are active or free within a guest-OS. The hypervisor only knows how much memory is allocated to a VM.

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