XenServer is an open-source server virtualization platform based upon the open-source Xen hypervisor (a type-1 / bare-metal hypervisor). XenServer is used for hosting virtualized server and client operating systems and provides performance comparable to that of bare metal servers.
The key features of XenServer are:
XenServer is developed by Citrix, who open-source the basic product. Citrix also offer a paid-for commercial version with enterprise support and a fuller range of features and management tools.
At various points in its history the commercial Citrix version of XenServer has been known as the “Citrix Hypervisor”.
A XenServer pool is a collection of standalone hosts that operate as a single resource: sharing identical hardware, identical setup, and the same shared resources. VMs deployed on one host can be readily migrated to another member host, and the pool master serves as the single point of management.
XenCenter is a Windows-based client software that enables users to install and manage XenServer environments. Using the XenCenter management console, you can install, provision and run virtual machines on a XenServer host.
The XenCenter Alerts view displays:
Xen Orchestra (XO) is an open-source web-based management platform for XenServer and the Xen hypervisor. It provides a comprehensive set of tools and features that simplify the management, monitoring, and automation of XenServer environments. Xen Orchestra is designed to enhance the administration and usability of XenServer, making it easier for users to manage their virtualized infrastructure.
Xen Orchestra is developed by a French third-party vendor Vates who offer a commercial, fully supported version which offers an alternative to Citrix’s commercial XenServer offering.
As with any virtualization technology, any failure of a XenServer hypervisor affects all the VMs running on it and the applications hosted on the VMs. Hence, monitoring of the XenServer hypervisor to ensure that it is working well is important. They types of issues that can affect a XenServer hypervisor include:
One of the key concepts of Xen is domains. “Domain 0” (Dom0) is the software portion that starts together with the server, an operating system with direct access to the underlying hardware that provides services to hosted machines and an admin management interface. In practice, Dom0 is a “specialized” Linux version that doesn’t just acts as a hypervisor, but also remains accessible for all management operations. Hosted VMs are active within a DomU (that U stands for Unprivileged) and must make requests via Dom0 for access to hardware resources, whereby Dom0 will translate or emulate such requests as appropriate.
Because Dom0 essentially runs a Linux OS, many applications designed for Linux can be run in dom0, an application added to the hypervisor in Dom0 is known as a kernel module. Commercially supported versions of XenServer supplied by Citrix do not support users adding applications to dom0 and strongly discourage the practice which is inherently less secure and can compromise hypervisor performance. So, whilst it is possible to add monitoring tools such as Nagios into Dom0, Citrix recommend the use of tools that consume XenServer metrics via supported interfaces validated via their Citrix Ready program. eG Enterprise is a Citrix Ready validated solution that does not compromise the integrity of Dom0.
Unlike XenCenter which only provides real-time performance insights, eG Enterprise includes a host of dashboards and reports that IT admins need. Furthermore, with integration to ITSM systems like ServiceNow, eG Enterprise automatically opens tickets in the ITSM tool whenever a problem is detected and auto-closes the ticket whenever a problem is resolved.
XenCenter and XenServer leverage RRDs (Round Robin Databases) to store performance metrics, to save and limit storage the RRDs are regularly consolidated, and older data becomes increasingly less granular. Many organizations with helpdesk operations and / or compliance auditing needs therefore choose a third-party monitoring tool to overcome the auditing and visibility limitations of the native RRDs.
To learn more about eG Enterprise monitoring for Citrix XenServer, please see: https://www.eginnovations.com/supported-technologies/citrix-monitoring/hypervisor-performance-management