Installation guide

Introducing XenServer

• Enhanced XenApp™ support: A dedicated XenApp VM template provides the fastest way to virtualize

XenApp installations.

1.4. What is XenServer?

XenServer is a server virtualization platform that offers near bare-metal virtualization performance for server

and client operating systems. XenServer uses the Xen hypervisor to virtualize each server on which it is

installed, enabling each to host multiple Virtual Machines simultaneously with guaranteed performance.

XenServer allows you to combine multiple Xen-enabled servers into a resource pool, using industry-stan-

dard shared storage architectures and leveraging resource clustering technology created by Citrix. In do-

ing so, XenServer extends the basic single-server notion of virtualization to enable seamless virtualization

of multiple servers as a resource pool, whose storage, memory, CPU and networking resources can be

dynamically controlled to deliver optimal performance, increased resiliency and availability, and maximum

utilization of data center resources.

XenCenter allows IT managers to create multiple clusters of resource pools, and to manage them and their

resources from a single point of control, reducing complexity and cost, and dramatically simplifying the

adoption and utility of a virtualized data center environment. With XenServer, a rack of servers can become

a highly available compute cluster that protects key application workloads, leverages industry standard

storage architectures, and offers no-downtime maintenance by allowing Virtual Machines to be moved while

they are running between machines in the cluster.

XenServer extends the most powerful abstraction: virtualization across servers, storage and networking

to enable users to realize the full potential of a dynamic, responsive, efficient data center environment for

Windows and Linux workloads.

By providing a unified view of the resources of one or more clusters of servers, and through its use of

a standardized abstraction for control of storage resources assigned to Virtual Machines, XenServer dra-

matically simplifies the job of the IT administrator seeking a painless solution for virtualization of demand-

ing production workloads. XenServer is ideally suited to users seeking to maximize the benefits of server

consolidation, automate test and development of software, or automate the assignment of resources and

protection of performance-sensitive production workloads.

1.4.1. Xen: the engine that powers XenServer

Xen provides fast, secure, open source virtualization that allows multiple operating system instances to run

as Xen Virtual Machines or VMs on a single physical 64-bit x86 computer. Xen supports modified guest

operating systems using a technique known as paravirtualization, which requires modifying the operating

system to run on Xen, but offers near-native performance. Paravirtualized operating systems "know" that

they are virtualized. Xen also supports unmodified operating systems using processor extensions from Intel

(VT) and AMD (AMD-V).

Xen supports 32-bit processors with and without Physical Address Extension (PAE), 64-bit processors,

and Symmetric Multiprocessing (SMP) guest operating systems.

Xen is exceptionally lean, which leads to extremely low overhead and near-native performance for VMs.

Xen re-uses existing Linux device drivers for Linux VMs, and uses special paravirtualized device drivers for

network and disk I/O on Windows VMs, making device management easy. Moreover, Xen is robust in the

event of device driver failure and protects VMs, and also protects the hypervisor from faulty or malicious

drivers.

Xen provides superb resource partitioning for CPU, memory, and block and network I/O. This resource

protection model leads to improved security because VMs and drivers are not susceptible to denial of service