Challenges in Monitoring XenServers
Xen enables administrators to implement two types of virtualization: para-virtualized VMs, which can enhance performance but require guest OS modifications, and fully virtualized VMs, which are highly portable and do not require guest OS modifications. With more and more IT environments these days turning to virtualization for easily and effectively managing their systems and resources, the flexibility that Xen offers in the implementation of virtualization makes it a coveted solution, especially for large infrastructures. Such infrastructures would typically have tens of virtual machines configured on a single XenServer host, with all VMs and applications sharing the physical CPU/memory/storage resources of the base XenServer host. In such infrastructures therefore, a resource contention at the host is bound to impact the resource allocation to the guests, thereby affecting the performance of the applications executing on the guests. Likewise, resource-intensive applications running on a VM can also drain the VM of the physical resources allocated to it. Therefore, whenever an application executing on a VM experiences a slowdown, administrators often take hours to determine where the root-cause of the problem lies - with the XenServer host or with the guest VM?
Moreover, the different virtualization deployment models pose different challenges. For instance, while the server application virtualization approach typically involves a smaller number of VMs running on a physical server, in the virtual desktop approach, tens of desktop VMs run on a physical server. The scale of deployment of desktops compounds the management troubles of administrators. In addition, while in-depth monitoring of each of the applications is important in the server application virtualization approach, monitoring of the desktop need not be as in-depth. Furthermore, in a virtual desktop environment, it is essential to identify which guest a user is logging on to, for how long the user was logged in, and what applications he/she used. This information is critical for planning the capacity of the virtual desktop environment.