I have a little bit of knowledge in working with VMware but I am still learning. I am trying to learn the performance aspects to better troubleshoot issues and optimize resource usage. We have a new Server 2008 R2 server with 32GB of RAM and it runs SQL 2008 R2. When we originally set it up, vSphere was showing ~25% usage while the OS showed ~50% usage. Since we had RAM to spare, we allocated some more to SQL. Now vSphere shows ~35% usage and the OS shows ~84% usage. Also, under the summary tab it shows 2.5GB active guest memory. Im just wondering why there is such a discrepancy? Does the vSphere chart show usage to total host memory? If that is the case, the numbers showing would make more sense.