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Farm terminology and concepts
Now is the moment to define the terminology which we are going to use in this book. If you are new in the XenApp world, please pay attention to this section. Except when noted, all following terminology applies to both XenApp 6.0 and XenApp 6.5.
- Multi-user environment is when applications are published on servers running Microsoft Remote Desktop Services and/or Citrix XenApp accessed by multiple users simultaneously.
- XenApp server is the main software component of the Citrix Application Delivery Infrastructure. The objective of XenApp servers is to deliver applications to user devices.
- XenApp application servers are the farm servers that host published applications, desktop, or content.
- XenApp infrastructure servers are the farm servers that host services such as a license server or Web Interface. Usually, they do not host published applications.
- Remote Desktop Services, formerly known as Terminal Services, is one of the components of Microsoft Windows Server 2008 and 2008 R2 that allow a user to access applications and data on a remote computer over a network. We need to install this component (and appropriate licenses) to set up and run XenApp servers. XenApp extends the functionality of Microsoft Remote Desktop Services, adding flexibility, manageability, security, and performance to RDS.
Applications can be made available by installing in the server or streaming to the client. Both XenApp 6.0 and 6.5 supports only Windows 32-bit or Windows 64-bit applications. Running 16-bit applications is not supported.
XenApp offers three methods for delivering applications to user devices, servers, and virtual desktops:
- Server-Side application virtualization: Applications run on the XenApp servers. XenApp shows the application interface on the user device or client, and transmits user actions from the device, such as keystrokes and mouse actions, back to the application.
- Client-Side application virtualization: XenApp streams applications on demand to the user device from the XenApp farm and runs the application on the user device.
- VM hosted application virtualization: Problematic applications or those requiring specific operating systems run inside a desktop on the XenApp server. XenApp shows the application interface on the user device or client, and transmits user actions from the device, such as keystrokes and mouse actions, back to the application. The application runs a XenDesktop or XenApp Server.
XenApp server farm is a logical collection or group of XenApp servers that can be managed as a single entity. Usually Citrix define three types of farms:
- Design validation farm: Design validation farm is set up in a laboratory, typically as the design or blueprint for the production farm. Usually the preferred method to build a design validation farm today is using virtual machines.
- Pilot farm: Pilot farm is a preproduction farm used to test a farm design and applications before deploying the farm across the company. The pilot must include users from the entire organization and role. These users should access the farm for their everyday needs.
- Production farm: Production farm is in regular use and accessed by all users in the organization.
Farm architecture defines the plan for the design of the server farm and zones based on current requirements and considers future expansion plans. Farm architecture requires a strong understanding of the network topology, scalability, failover, and geographic location of the sites and users in the company.
- Zones: Zones are used to control the aggregation and replication of data in the farm. A farm should be divided into zones based upon the network topology, where major geographic regions are assigned to separate zones. Each zone elects a data collector, which aggregates dynamic data from the servers in its zone and replicates the data to the data collectors in the other zones. Citrix recommends to create no more than 25 Zones.
- Worker Group: A Worker Group is a new feature introduced on XenApp 6.0, also available on XenApp 6.5. It is a collection of XenApp servers in the same farm. Worker Groups allow a set of similar servers to be grouped together and managed as one. Worker groups are closely related to the concept of application silos (silos usually are servers dedicated to run critical or resource intensive applications). All servers in the Worker Group share the same list of published applications and identical XenApp server settings.
- Server roles: XenApp 6.5 introduces new server roles: session-host (also known as session-only) and session-host and controller (also known as controller) roles and the ability to create either controller or session-host only servers. In previous versions of XenApp, including version 6.0, all servers were having/must have both roles and we can't split them.
When we choose the controller mode, servers act like previous versions of XenApp: they can host sessions, the XML services, provide application enumeration, force data collector elections, and so on.
On another hand, running XenApp servers in session-host mode improves start-up and join performance, which is especially recommended for servers running in different zones, branch office, or remote sites. This is because servers running in Session-only mode require less read/writes to the Data store during a join or sync process, which reduces bandwidth and resource usage on the Data store server. We are going to continue learning about server roles in the next chapter.
- Data Collector: Data Collector server stores information about server load and published applications inside a zone and acts as a gateway between Data Collector servers in other zones. In large XenApp server farm environments, it is a good idea to have a primary dedicated data collector server and backup data collector. Also it is recommended to restrict the primary data collector from delivering applications. A dedicated Data Collector improves load balancing decisions and reduces session logon time. We can use a small virtual machine or small server for the dedicated data collector role. XenApp 6.5 introduces the controller role (see above) and when designing our farm, data collectors must be set always as controller role.
User device is where the client software is installed to access data anywhere:
- Citrix Receiver: Citrix Receiver is the first universal client for IT service and netbooks (PC or Mac).With Citrix Receiver installed on a device, IT can deliver applications and desktops as an on-demand service with no need to manage, own or care about the physical device or its location. Citrix Receiver is a lightweight software client with an extensible browser-like "Plug-In" architecture. Citrix Receiver was formerly known as Citrix ICA Client.
- Citrix Dazzle and the Self-service storefront: Citrix Dazzle, the self-service enterprise application storefront, offers a personal and easy-to-use interface for subscribing to applications. Administrators can distribute the Dazzle plugin using Citrix Receiver, and users can choose their published application subscriptions. Dazzle also downloads and pre-caches streamed applications. The self-service storefront is available for both Windows and Mac users.
- Merchandising Server provides easy management, setup and distribution of Citrix Receiver and related plugins and updates. Users simply point any browser to the setup site included with Merchandising Server and within two clicks the setup process starts. Merchandising Server software is delivered as a virtual appliance for Citrix XenServer or VMware.
Infrastructure servers
Infrastructure servers are farm servers that host services such as a license server or web interface. Usually, they do not host published applications.
XenApp farms have two types of infrastructure servers:
- Virtualization infrastructure consists of the XenApp servers that deliver virtualized applications and VM hosted applications, and roles that support sessions and administration, such as the data store, data collector, Citrix XML broker, Citrix License Server, Configuration Logging database (optional), Load Testing Services database (optional), and Service Monitoring agents, and so on.
- Access Infrastructure consists of roles such as the Web Interface, Secure Gateway (optional), and Access Gateway (optional) that provide access to users.
In small deployments, we can group one or more roles together. In large deployments, we can provide services on one or multiple dedicated servers.
Virtualization infrastructure represents a series of servers that control and monitor application environments.
Now, we will see different types of infrastructure servers:
- Citrix Licensing: A Citrix License Server is required for all XenApp deployments. Install the license server on either a shared or standalone server, depending on our farm's size. After we install the license server, we need to download the appropriate license files from the MyCitrix.com website and install them in the license server. We can share a license server with multiple Citrix products. We are going to install and configure a license server in the next chapter.
- Data Store database: Also known as IMA Data store, is a repository of persistent farm information, including server's information, published applications, administrators, printers, and so on. We can host the Data Store database on a SQL Server Express database running on one of our XenApp servers in a small or test farm, or use a dedicated SQL Server or an Oracle database server in medium to large farms. If XenApp servers are running in multiples zones, we need to host the Data store in the largest site. We are going to install and configure a Data Store in the next chapter.
- Citrix XML Broker acts as an intermediary between the Web Interface and other servers in the farm. When a user logs in into the Web Interface, the XML Broker receives the user's credentials from the Web Interface and queries the server farm for a list of published applications that the user has permission to access. The XML Broker obtains this application set from the IMA (Independent Management Architecture) system and returns it to the Web Interface.
- Citrix XML Service: The XML Broker is a component of the Citrix XML Service. By default, the XML Service is installed on every server during XenApp setup. However, only the XML Service on the server specified in the Web Interface acts as the broker. In a small farm, the XML Broker runs on a server with multiple infrastructure functions. In a large farm, the XML Broker might be configured on one or more dedicated servers. Configuring a dedicated XML server is a simple task, we need to set up a dedicated XenApp server without any published applications.
- Single Sign-on(optional): Single Sign-On provides password management for published applications. Single Sign-on can use Active Directory or a NTFS share to store password information. Single Sign-on was formerly known as Password Manager and requires a Platinum license. Installation and configuration of Single Sign-on is beyond the scope of this book.
- Service Monitoring(optional) is based on Citrix Edgesight and enables the administrator to collect, monitor, and report server resource metrics to estimate servers required to deploy a XenApp farm or to analyze the load of production servers. This feature requires a Platinum license. Installation and configuration of Edgesight is beyond the scope of this book.
- Provisioning Services(optional) assist administrators to manage the entire XenApp farm of application hosting servers, both physical and virtual, using one or multiple standardized server image(s). PVS can rollback to a previous working image in the time it takes to reboot.This feature requires a Platinum license. Installation and configuration of Provisioning Services is beyond the scope of this book.
- SmartAuditor(optional) allows administrator to record the onscreen activity of any user's session, over any type of connection, from any server running XenApp. SmartAuditor uses policies to record, catalog, and archive sessions for retrieval and playback. This feature requires a Platinum license. Installation and configuration of SmartAuditor is beyond the scope of this book.
- Power and Capacity Management (optional) enables administrators to reduce power consumption and manage server capacity by dynamically scaling the number of online servers or powering on/off servers based on specific times. This feature requires a Platinum license. Installation and configuration of Power and Capacity Management is out the scope of this book.
Access Infrastructure represents a series of servers deployed within the local network or the DMZ (Demilitarized Zone) to provide access to different types of users (local or remote) to resources published on XenApp servers.
XenApp farms have three types of access infrastructure servers:
- Web Interface provides users access to resources published on one or multiple XenApp farms through a standard Web browser or through the Citrix Receiver (formerly known as Citrix Online Plug-I). The new Citrix CloudGateway released in January 2012 is going to replace Web Interface on upcoming versions of XenApp. Web Interface end of life is planned for 2015.
- Access Gateway(optional) is a universal SSL VPN appliance that can be used to secure client connections to XenApp farms and provide secure access to other internal network resources. XenApp Platinum Edition licenses include a universal Access Gateway license, which can be used with any Access Gateway edition. The Access Gateway appliance, also known as NetScaler must be purchased separately.
- Secure Gateway(optional) assists administrators to secure access to enterprise network computers running XenApp and provides a secure Internet gateway between XenApp farms and client devices. The Secure Gateway transparently encrypts and authenticates all user connections to help protect against data tampering and theft. All data traversing the Internet between a remote workstation and the Secure Gateway is encrypted using the SSL (Secure Sockets Layer) or TLS (Transport Layer Security) protocol.The Secure Gateway is an application that runs as a service on a server that usually is deployed in the DMZ. The free Access Gateway VPX available as Virtual Machine is the natural replacement for Secure Gateway.