Citrix an Enterprise Solution or an Illusion?

Citrix an Enterprise Solution or an Illusion?

One year and half ago, I was tasked with a major project, and one part of this project was to have Citrix implemented, to allow secure remote access.

 Citrix seemed an interesting solution and I was keen to learn more about it and start to work with it.

Knowing what I know now, I am going to make an statement; Citrix depends on far too many third party products and if it is not well planned, well designed and well implemented, it will become a headache.

Citrix Dependencies (to name few):

• Windows
• Terminal Services
• Internet Information Services
• SQL Server
• Group Policies
• Active Directory
• Browsers (i.e IE)

Note: This depends on the design and implementation.

Problems as I see
Databse
The Citrix farm is controlled by central Database Server, changes to the farm are all controlled and dependant on this central data base.
It is a small databse, but if the correct solution for this Server is not taken into account, it may become a problem.

Depending how resilient you want the Citrix system and how available you need it, you need to take a look at this part of the system carefully.
If you have multiple sites, take extra care where positioning the database server.
If you decide to use Database Mirroring with witness, keep an eye on your witness, where you will position it. If your Principal loses quorum your farm will be rendered unmanageable.

Citrix License Server
Citrix has a License server, which as far as I am aware must be installed otherwise Xervers will not be available for connection.
Be very careful where you position your License Server, if you have multiple sites make sure you position your Citrix license server in the best site possible. Monitor its availibility. Make sure all servers can reach it.

Licenses
Choose your license model carefully, per user or per device. For what I understand if you use per device, each device requires a license and if you have users with multiple devices i.e. iPads, iPhones, PCs, Laptops. I would say per user is more cost effective, but I would discuss the options with your Citrix designer or consultant.

Note: Citrix has a policy to set the License server and the defaul port for the whole farm.
Make sure TCP PORT 2700 is not blocked by firewalls.
There are also two registry keys which are set on each XenApp Server to point to the License server.

Terminal Services License Server
As Citrix runs on top of TS it depends on Terminal Services and Terminal Services require Licenses, once again per user or per device.
Be careful where you place your Terminal Services License Server, if it is not available, new users won't be able to log on to your Citrix system.

There are many options to make it resilient and redundant, in case of multiple sites.
You can setup dual License servers and split all the licenses per server, for example.

I think understanding the  pitfalls and how you can over come them is important, if I had this knowledge when I started implementing Citrix, things would be different.

Be aware and just open the discussions with your Citrix specialist, don't wait for them to guide you, they are more interested in selling.

Citrix Webinterfaces
One of the Citrix roles is the web interface, this is the server which presents the webpage asking each user to identify themselves, with username and password.

Again, take extra care on with this server. Depending on how many users you have on your farm or organization, you may need more than one.
If your organization requires redundancy, you will centainly need more than one. Where you place them is also important, if your users are crossing a leased line to access your Citrix WI servers, you need to make sure a) the leased lines are resilient b) you have a back link c) or you have multiple WIs in each location.

XenApp v XenDesk
It all depends on your needs. If you have applications which need to be made available to your users via Citrix, I think it makes more sense to make use of XenApp.

On the other hand if you have multiple users and each user requires a desktop, then using XenDesk makes more sense.

Both options have pro and cons, sometimes you will need a mix of both. Keep your eyes open and discuss your needs with your Citrix consultant.

If you have a bunch of developers and each one needs their own environment, I think XenDesk makes more sense. If your users tend to use heavy applications, sharing a desktop with another heavy user is no fun and can cause loss of productive to both users.

As you can see there are many aspects of a Citrix System which are not quite clear cut and also depend on many external variables.
I don't think it is an easy solution to troubleshoot either.

Recently I had a massive problem where both systems where unavailable and each part of the system presnted me different prpblems.
I will write about these problems in the next posts.

I hope this post will be helpful to you in deciding in using Citrix or not, and if you do decide to use, it will be helpful in giving you some ideas on how to best approach it.

Note: I am not a Citrix expert, I am writing about my experience so far with Citrix and I do advise you, look for a good consultant. Check references, past projects and talk to customers to make sure their work was implemented successfuly.

By Renato de Oliveira