Monitoring Memory Usage
Monitoring memory usage, whether on a host or a VM, can be challenging. The monitoring itself is not difficult; it's the availability of the physical resource that can be a challenge. Of the four resources, memory can be oversubscribed without much effort. Depending on the physical form factor chosen to host VMware ESXi, running out of physical RAM is easy to do. Although the blade form factor creates a very dense consolidation effort, the blades are sometimes constrained by the amount of physical memory and network adapters that can be installed. But even with other regular form factors, having enough memory installed comes down to how much the physical server can accommodate and your budget.
If you suspect that memory usage is a performance issue, the first step is to isolate whether this is a memory shortage affecting the host (you've oversubscribed physical memory and need to add more memory) or whether this is a memory limit affecting only that VM...
