User guide

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responsible for delivering desktops or applications, to a dedicated server. If the primary data collector were
to fail, a backup, with the same hardware and software configuration, should also be available. Similar to
Web Interface, providing fault tolerance to the Data Collector servers is recommended.
◦ Data Collector (Dedicated XML Server): A Data Collector acting as a dedicated XML server allows
the master Data Collector to focus on farm management while directing the Web Interface servers to
communicate with the XML servers. The XML broker is responsible for user authentication, resource
enumeration and resource launching processes. A failure in the XML broker service will result in
users being unable to start their desktop. Due to its criticality it is best to have at least two dedicated
XML servers.
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Load Managed Groups: Whether delivering applications or desktops, organizations might create load
managed groups based on business requirements. Load managed groups are created to focus a set of
XenApp servers on a particular set of applications or desktops. This is done for numerous business and
technical reasons including update frequency, business unit server ownership, criticality, regional access,
and language requirements.
When creating a load managed group, each group must provide enough redundancy to be capable of
supporting all users in the event of a server failure. This results in an N+1 scenario where there is at least
one additional XenApp server per load managed group. In many situations, organizations implement an
N+10% strategy where an additional 10% of XenApp servers per load managed group are allocated in
order to allow for multiple server failures or maintenance.
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License Server: The license server receives license check-in and check-out requests from the XenApp
server in the same fashion as XenDesktop. This service is fairly lightweight and has a grace period for
XenApp licenses which allows the system to function normally if the license server becomes unavailable.
This grace period offsets the complexity involved with building redundancy into the license server.
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Data Store: Each XenApp farm requires a database called a data store. Citrix XenApp uses the data store
to centralize configuration information for a farm in one location. The data store maintains all the static
information about the XenApp servers, applications and administrators in the server farm.
Citrix XenApp plays a critical role in providing an end-to-end virtualization solution. XenApp is fundamentally
based on the ability to provide multiple users with access to an independent instance of an application or desktop
on a single XenApp server with the popularity previously focused on application virtualization. Before Windows
Server 2008 R2, the published XenApp desktop was a server desktop, but now with the release of the Desktop
Experience Feature of Windows 2008 R2 a server desktop can be customized with the look and features of a
Windows 7 desktop therefore empowering the XenApp virtual desktop delivery model of Hosted Shared desktops.
Given the ability to XenApp to provide both virtual desktops and applications, the following sections outline the
order of operations required to access a virtual desktop hosted on XenApp and the ability to launch a virtualized
application hosted on XenApp from within a virtual desktop.