Agent Deployment Models
As mentioned earlier, administrators can choose between the agent-based and agentless approaches to Xen monitoring. In case of the “agent-based” approach, a single eG agent deployed on the control domain (i.e., Domain 0) of the XenServer can be configured to monitor the host and each of the guest operating systems executing on it (see Figure 1). The control domain of the XenServer runs a Linux variant. Hence, the eG agent for Linux should be deployed on the XenServer. When installing the eG agent, make sure that you have at least 350MB of free disk space on Domain 0. The procedure for deploying the eG agent on the control domain is exactly the same as the process for installing the eG agent on Linux, which is described in the eG Installation Guide.
In case of the “agentless” approach, an eG agent deployed on a remote Windows or Linux host in the environment can be configured to monitor the loading of the physical XenServer, the relative loading of each of the guests on the server, and how well each guest is using the resources allocated to it (see Figure 2). Refer to the eG Installation Guide for a detailed procedure on how to install and configure an eG agent on Windows/Linux.
Figure 1 and Figure 2 clearly indicate that the eG agent (whether on a control domain or on a remote Windows/Linux host) remotely communicates with each guest via SSH/WMI (depending upon the virtual OS in use) to obtain the “inside view” of the guests. To establish this remote connection with Windows VMs in particular, eG Enterprise requires that the eG agent be configured with domain administrator privileges. In high-security environments, where the IT staff might have reservations about exposing the credentials of their domain administrators, this approach to extracting “inside view” metrics might not be preferred. In such environments therefore, eG Enterprise provides administrators the option to deploy a piece of software called the eG VM Agent on every Windows VM, which allows the eG agent to collect “inside view” metrics from the VMs without domain administrator rights. Refer to the Configuring Windows Virtual Machines to Support the eG Agent’s Inside View Using the eG VM Agent for more details on the eG VM Agent.