Citrix® XenApp environments have grown in popularity as cost-effective, efficient modes of accessing a variety of heterogeneous applications on-demand. In order to be an effective alternative for desktop applications, Citrix XenApp environments must deliver the same quality of service that users have come to expect from local applications.
A typical Citrix XenApp server infrastructure
Typically, Citrix server farms include multiple tiers of software. A front-end web interface (Nfuse) server is used to support web-based accesses to the server farm. Active directory servers handle user authentication and rights association, while user profiles are loaded from profile servers. The authenticated requests are passed to the Citrix XenApp (Presentation) servers that host a number of applications. In turn, the applications may use backend databases, printers, etc., for different functionalities.
While Citrix-based access infrastructures offer economies of scale, there are significant challenges in monitoring Citrix XenApp server farms.
Citrix XenApp Performance is ImportantA XenApp server failure is catastrophic :
In a typical Citrix infrastructure, all the processing is done on the XenApp servers. Hundreds of users may be accessing the Citrix farm. Hence, even a transient problem in the farm can impact all the users accessing the farm. Furthermore, since different applications are hosted on the same server, a performance problem (e.g., a memory leak) with one application can adversely impact the performance of all the other applications hosted on the server. Likewise, since multiple users access applications on the same server, a rogue user can impact the performance of all the other users accessing the Citrix XenApp server.
Performance of All the Tiers Impacts Citrix PerformanceCitrix XenApp infrastructures are distributed, heterogeneous, and multi-vendor :
Users access a Citrix farm from different geographic locations, over WAN links. The users may be logging in from different networks, using different client terminals. For the Citrix service to function well, all the applications and devices involved in service delivery must perform well. Therefore, monitoring network devices and links, Active Directory servers, Citrix XenApp servers, backend applications. database servers, etc. becomes all the more critical.
End-to-End Monitoring is Essential to Manage the Citrix User ExperienceCitrix service delivery involves multiple inter-dependent applications :
Owing to the multi-tier nature of Citrix environments, a slow-down in one tier (e.g., the authentication server) can cause a slow-down of the entire service. When a slow-down occurs, an administrator of the Citrix farm has to quickly determine what the source of the problem could be - i.e., Is it the network? Or the web interface server? Or the Active Directory server? Or the profile server? Or the Citrix XenApp server? Or the backend database? Accurate, fast diagnosis of problems helps reduce downtime of Citrix services, enhance the Citrix user experience, and improve customer satisfaction.
Limitations of a silo-based approach to Citrix monitoring: A slowdown in one tier (e.g., the database) can impact all the other tiers (e.g., the web server, Citrix XenApp server). By monitoring the Citrix server and other tiers individually, it is not easy to determine where the real problem lies.