Monitoring performance is a key part of every vSphere administrator's job. Fortunately, vCenter Server provides a number of ways to get insight into the behavior of the vSphere environment and the virtual machines running within that environment.
The first tool vCenter Server provides is its alarms mechanism. Alarms can be attached to just about any object within vCenter Server and provide an ideal way to proactively alert the vSphere administrator about potential performance concerns or resource usage.
Another tool that vCenter Server provides is the Resources pane on the Summary tab of both ESX/ESXi hosts and virtual machines. This Resources pane provides quick ''at-a-glance'' information on resource usage. This information can be useful as a quick barometer of performance.
In addition to the graphs and high-level information tabs, the administrator can create alarms for virtual machines, hosts, networks, and datastores based on predefined triggers provided with vCenter Server. Depending upon the object, these alarms can monitor resource consumption or the state of the object and alert the administrator when certain conditions have been met, such as high resource usage or even low resource usage. These alarms can then provide an action that informs the administrator of the condition by email or SNMP trap. An action can also automatically run a script or provide other means to correct the problem the virtual machine or host might be experiencing.
The creation of alarms to alert the administrator of a specific condition is not new in this version of vCenter Server. But the addition of new triggers, conditions, and actions gives the alarms more usefulness than in previous editions. As you can see in Figure 12.2, the alarms that come with vCenter Server are defined at the topmost object, the vCenter Server object. You'll also note that there are far more predefined alarms in vCenter Server 4 than in previous versions of vCenter Server or VirtualCenter.