Microsoft Licensing for Citrix:
This is part 3 of a series on this subject. Part 1 went through the Microsoft licensing components required for all the various Citrix implementation possibilities, while Part 2 described the Microsoft licensing contract options. This part will describe the various Citrix delivery options and how this affects Microsoft licensing.
In our opinion, Citrix made a real marketing mistake by calling their combined product XenDesktop. The reason for this is that XenDesktop Enterprise and Platinum licenses also include the ability to run XenApp as well as XenDesktop VDI, or both delivery methods, for each user. We think they should have called it XenSuite, as that more appropriately describes the product’s capabilities and is far less confusing to the uninitiated. Be that as it may, application and desktop virtualization is not a one-size-fits-all solution, so it is a very powerful feature to be able to do both types of delivery. This installment will describe all the popular combinations, along with their benefits and drawbacks.
This is where Citrix started, although it used to be called WinFrame, then MetaFrame, then Presentation Server, and finally XenApp. That’s the overactive marketing department at Citrix striking again. Originally, this solution was based on physical servers and a copy of Windows 2000 or 2003, and a typical dual CPU, 4GB RAM pizza box server was good for 40-50 simultaneous users. Now, with the coming of Windows 2008r2 and subsequent 64-bit versions of their server OS, it is common to see 100-150 simultaneous users on that same 2 CPU server. Naturally, the CPUs are much stronger, but the biggest boost was the 64-bit Windows OS. Furthermore, close to 100% of all new Citrix server implementations these days are as virtual servers on VMware, XenServer or Hyper-V. They all work very well, so choose the one that suites you the best.
- Very low-cost through greater density on a given set of hardware.
- Only Microsoft RDS CALs are required, regardless of the workstation used.
- Few moving parts leads to easier support.
- The technology is based on a published hosted desktop (or application), and some apps don’t play well.
- Slightly less granular control over the server priorities that with VDI.
- Slightly different look and feel to the users that VDI with is Windows 7/8 to them.
We still use XenApp as the default standard as its advantages far outweigh its drawbacks and most cases.
XenDesktop VDI or VDI-in-a-Box Alone
As most of you know, Citrix offers two flavors of VDI solution. VDI-in-a-Box uses servers with local disk and is easy to setup and administer. It is a very good solution for smaller implementations (250 users or less). XenDesktop VDI is Citrix’ enterprise solution and it is almost infinitely scalable. For the most part, the advantages and disadvantages apply to both variants
- True Windows 7/8 desktop (not a Windows server 2008 shared desktop) so user acceptance is good.
- Compatible with virtually all applications.
- Users can be allowed to load their own apps, and make other modifications if desired.
- No SAN required (VDI-in-a-Box).
- Many moving parts in the solution leads to more difficult support.
- Take roughly twice the server hardware to support a given set of users over XenApp.
- Performance is sometimes sluggish due to the heavy environment demands.
- User image space requirements lead to a LOT of disk.
- Microsoft takes a BIG bite with VDA licenses as an annual fee, or uses this to force companies to an Enterprise agreement that includes that capability.
With the advent of several new in RAM disk technologies, two of the three main drawbacks (performance sluggishness and large disk requirements) have been made complete non-issues. Key files are store on RAM disk making the session lightning fast, and image size requirements are also dramatically reduced as the in RAM tools also have dedupe and disk compression technology that compresses images as much as 95%. Because of this, and because of the ability to aid customers in their transition off of Windows XP at the workstation, VDI solutions have been very hot in the last year.
XenDesktop VDI and XenApp Combined
Citrix has the unique ability to be able to offer both XenDesktop VDI and XenApp in the same solution. Why would you want to do that? One key reason… to keep VDI Images smaller. You can create an image with all the key applications, or you can create stripped down image with a Citrix client, a browser, and PDF reader, and then feed the other applications to it from XenApp. This reduces the RAM requirements on the VDI host since the images are smaller, and it also reduces the processing load since the XenApp-fed applications are actually running on the XenApp server, which we know is more efficient. What we see most companies doing is putting their key applications in the image, and using XenApp for the lesser used or troublesome apps.
- Best of both worlds in terms of efficiency and flexibility.
- Will require less hardware that a VDI only solution.
- The most complicated of the environments to manage and support.
- Will probably require an RDS CAL and a VDI License, or an Enterprise agreement L.
This is the best practices solution with ultimate flexibility, but it is expensive on until you really reach economies of scale (400+ users). It is pretty much an enterprise-only class of solution.
All three solutions are now very viable, and most of the key drawbacks have been eliminated from all of them. Furthermore, there are profile and image management products that streamline the implementation even further, and monitoring/management products that allow you to manage it very effectively. Combine that with 64-bit server OSes and powerful hardware, and desktop virtualization of any variety, is looking pretty good these days.