Information Technology Reference
In-Depth Information
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 i rst 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 (meaning you
need to allocate more memory to this VM or change resource allocation policies). Normally, if
the ESXi host is suffering from high memory utilization, the predei ned vCenter Server alarm
will trigger and alert the vSphere administrator. However, the alarm doesn't allow you to delve
deeper into the specii cs of how the host is using memory. For that, you'll need a performance
chart.
Perform the following steps to create a real-time chart for a host's memory usage:
1.
Connect to a vCenter Server instance with the vSphere Web Client.
2.
Navigate to Hosts And Clusters view.
3.
In the Navigator, click an ESXi host. This shows you the Summary tab.
4.
Click the Performance tab, and switch to Advanced view.
5.
Click the Chart Options link.
6.
In the Chart Options dialog box, select the Memory resource type and the Real-Time dis-
play interval.
7.
Select Line Graph as the chart type. The host will be selected as the only available object.
8.
In the Counters area, select the Memory Usage (Average), Memory Overhead (Average),
Memory Active (Average), Memory Consumed (Average), Memory Used by VMkernel,
and Memory Swap Used (Average) counters.
This should give you a fairly clear picture of how much memory the ESXi host is using.
9.
Click OK to apply the chart options and return to the Performance tab.
Counters, Counters, and More Counters
As with VMs, you can utilize a plethora of counters with a host to monitor memory usage. Which
ones you select will depend on what you're looking for. It is common to monitor straight memory
usage, but don't forget that there are other counters that could be helpful, such as Ballooning,
Unreserved, VMkernel Swap, and Shared, just to name a few. h e ability to assemble the appro-
priate counters for fi nding the right information comes with experience and depends on what is
being monitored.
