XenServers

XenServer, now known as Citrix Hypervisor, is a virtualization platform for server environments built around the Xen Project hypervisor. It enables the creation, running, and management of multiple virtual machines on a single physical server, supporting consolidation and flexible resource use in data centers and service providers.

XenServer provides paravirtualized and hardware-assisted virtualization for guest operating systems, with a management stack that includes a graphical console and a command-line interface. It supports features such as live migration of running VMs between hosts in a pool, high availability, dynamic memory control, storage integration with shared storage, iSCSI, and templates for rapid VM provisioning. The platform includes XenTools to improve performance and integration for Windows and Linux guests.

The core architecture uses the Xen hypervisor as the underlying layer, with a management domain (Dom0) running XenServer's control software and one or more guest domains (DomUs) that host the operating systems. Administrators can configure host pools, allocate resources, and manage snapshots and backups through the management tools. XenServer supports a range of guest operating systems, including various Linux distributions and Windows, with both 32- and 64-bit variants depending on hardware.

It has historically offered a free edition with basic virtualization features and paid editions providing advanced management capabilities and support. Citrix later rebranded XenServer as Citrix Hypervisor, maintaining the core virtualization technology while extending management features and cloud integration for organizations using Citrix virtualization solutions.