I don't know how many situations I've been in where a simple and most importantly free system monitor would have saved a lot of headache and strife. You just can’t beat free monitoring tools. For those of you who dabble in ESX from time to time, you know that staring at the VI client as a monitoring method can become a bit overwhelming (not to mention boring.. at least if you set things up correctly... but I digress). A monitoring tool that meets all of the aforementioned specs is SolarWinds VM Monitor (VMM). It keeps tabs on an ESX server and alerts you in the event of a problem. Even when there isn’t a problem, you still get the ability to see what is going on in the virtual environment.

The installation is pretty simple. You install VMM, enter the IP address or name of your ESX server when prompted, as well as that server’s read-only SNMP string. The screenshot shows that you can see that nine of 10 installed VM's are running but one VM is in a critical state due to the guest CPU running at full-throttle. Notice that the critical VM's CPU is running at 100%. ESX's CPU is still running at only 16% capacity. You also get to view the memory utilization for both the guest VM's as well as the ESX server (and all running VMs) in total. A tool such as VMM combines information in a way that is useful in helping you to decide what resource utilization strategy to implement in order to optimize your configuration.

As you may know with most free software, there's always a catch. In this case, here are its core limitations:

• It is limited to monitoring a single ESX server
  
• For each virtual machine, only a few high-level performance statistics are monitored

The catch here is that SolarWinds would like you to purchase their Orion full-fledged monitoring product to gain all of the monitoring features available. They also have additional products and suites available for other purposes if you want to take a look at their offerings.