Choosing between XenDesktop and XenApp for desktop virtualization

Citrix XenApp offers virtual desktops, a lower TCO, lower total cost of acquisition and less complexity than XenDesktop so why would anyone choose XenDesktop?

Of course there are several reasons to choose XenDesktop, but in many cases XenApp is the less expensive desktop virtualization product. By less expensive I mean a lower TCO and lower total cost of acquisition and not the per concurrent user cost which is higher with XenApp.
For all the reasons listed above I would start out investigating using XenApp for all your users and then look to use XenDesktop for the users that require any of the following functionality.

1. Generic USB Support
   
2. Native Windows XP or Vista Explorer Interface
   
3. Virtual Desktop Isolation
   
4. Application Compatibility
5. OS Streaming Directly to the Desktop
6. Enhanced Multiple Monitor Support
7. Enhanced Smartcard Support
8. User-driven Desktop Restart
9. Bitmap Remoting (Future)
10. Offline Desktops (Future)

Generic USB Support
XenApp supports printers through client printer mapping, scanners through TWAIN, USB flash drives and PDA synchronization (Active Sync). But there are still many USB devices not covered by XenApp that are covered with XenDesktop's generic USB support. Currently real time (isochronous) devices such as web cams are not covered, but hopefully they will be supported in the future.

Native Windows XP or Vista Explorer Interface
The XP and Vista explorer interfaces are more user friendly than the Windows Server shared desktop provided by XenApp. You can make a XenApp published desktop look more like XP using the Luna theme, but some users may insist on having the exact same explorer interface provided with XP or Vista.

Virtual Desktop Isolation
A single XenApp user can consume a large portion of the processor and memory resources effectively starving resources for the other users. XenApp offers CPU Utilization Management to help with evenly distributing processor cycles.
Isolating the desktop also protects against system crashes that can blue screen the server. However the majority of crashes only affect an application which would not disrupt other sessions on the XenApp server.

Application Compatibility
With XenApp all your applications must run on Windows Server. XenApp does offer Isolation 2.0 and Application Isolation Environment (except for Windows Server 2008) that can help run troublesome applications. But there are still some applications that will only run on XP or Vista.

OS Streaming Directly to the Desktop
XenDesktop has the ability to stream the OS directly to the client device via the desktop provisioning component. This allows the user to take full advantage of the CPU, GPU, and memory on their client device.

Enhanced Multiple Monitor Support
XenDesktop supports up to 8 monitors and is not limited by the Windows Server video buffer. By default XenApp has a limited buffer but you can make registry changes and/or use additional tools such as Virtual Display Manager

Enhanced Smartcard Support
Both XenApp and XenDesktop support smart cards including Common Access Card. However XenDesktop supports additional functionality such as USB smart card tokens.

User-driven Desktop Restart
If a XenApp server is unresponsive a users only recourse is to logoff / disconnect and login again. However the user might be assigned to the same troublesome server. With XenDesktop if you have any problems with your virtual desktop you can perform a remote restart.

Bitmap Remoting (Future)
As shown by Derek Thorslund's blog on HDX, XenDesktop will have bitmap remoting. This will allow complex graphical applications to be run on the virtual desktop and remoted via bitmaps to the client device. Note that until GPU virtualization is available, bitmap remoting is only useful for blade CPs.

Offline Desktops (Future)
The idea with offline desktops is that a user can "check out" his centralized virtual desktops to his local laptop or PC. This local virtual desktop can be used in an offline mode while the user does not have access to the network. After the user is finished he can upload his virtual desktop
including any changes to the datacenter. Now the user can once again access his centralized virtual desktop from his thin client or whatever client device he was using. For more information see Project Independence.


There are a few features in XenApp that are not present in XenDesktop
1) Enhanced scalability of about 5X to 7X number of users per server.
2) Quicker and easier to implement.
3) Speedscreen latency reduction to allow for interactive typing over slow WAN connections.

XenApp also currently has an advantage with VOIP, but over time that advantage will probably disappear.

So what do you think? What did I get right? What features are missing?

Free XenServer Makes XenDesktop Shine

Citrix recently announced they will have a free enterprise version of XenServer. Based on their feature chart this free XenServer version is the same as the older XenServer Enterprise edition with HA and direct storage integration removed. Since XenDesktop includes XenServer as the default virtualization platform what does XenServer now being free mean to XenDesktop?

First XenDesktop Standard included XenServer Standard which does not offer resource pooling. The Desktop Delivery Controller (DDC) in XenDesktop can connect to XenServer but only versions that offer resource pooling. So now with a free enterprise version of XenServer and XenDesktop Standard, the DDC can communicate with XenServer to provide functionality to start/stop/suspend/resume the virtual desktops.

Second VMware Infrastructure controls most of the market for server virtualization especially among large enterprises. This translates to most XenDesktop deployments running on top of VMware Infrastructure. As I discussed in an earlier post the customer will need to pay $200 to $300 retail per user to VMware with XenDesktop being an additional cost. VMware's desktop virtualization product, View, is not too far behind XenDesktop in functionality and is price around $250 per user for the enterprise version that includes VMware Infrastructure. With this price savings customers will look heavily to an all VMware solution.

With a free XenServer, Citrix has the ability to gain market share in the server virtualization market especially for XenApp on XenServer deployments since XenServer performs better than VMware Infrastructure for XenApp workloads. With XenDesktop Enterprise and Platinum customers no longer need to pay extra to virtualize the XenApp component as part of XenDesktop. These moves are crucial to get customers to fragment their data center to have more than one virtualization infrastructure. With customers trained on XenServer, it is a small step to convince customers to run XenDesktop on XenServer instead of VMware Infrastructure. When customers use XenServer instead of VMware for their XenDesktop deployment the customer saves a significant amount of money ($200 to $300 per user) since the customer is not paying for VMware Infrastructure.

XenServer never brought in the desired revenue for Citrix so making XenServer free is a smart move. It gives them an opportunity to capture a significant portion of the market and erode VMware's virtual monopoly on server virtualization. It also positions XenServer competitively vs. Hyper-V since Citrix is now the cheaper alternative and offers more features and functionality.

Any questions, comments, or ideas for additional posts are appreciated.

Cashing in on Desktop Virtualization

Centralized virtual desktops promises to lower TCO and improve employee productivity. The technology leader in this space is Citrix XenDesktop with VMware View close behind. They probably have about the same market share and all of the virtual desktops are running Microsoft XP or Vista.

Let's take a look at what is becoming a very common configuration - Citrix XenDesktop Enterprise running on top of VMware Virtual Infrastructure (VI) with Microsoft XP/Vista virtual desktops. So Citrix is providing the desktop virtualization infrastructure, VMware is providing the virtualization platform and Microsoft is providing the desktop OS.

So for three year software licensing costs.

Citrix XenDesktop Enterprise is $295 per user plus $15 per year after the first year to stay current with updates. The three year cost would be about $325 retail.

Microsoft XP/Vista costs will vary considerably but if you are using thin clients the annual costs are about $120. This is for a VECD license without SA. A Terminal Services CAL is also required at a one time cost of $120 in order to use the XenApp for VDI component in XenDesktop. The three year cost would be $480.

VMware Virtual Infrastructure (VI) is used in almost all large companies for server virtualization. So these companies are choosing to use VMware VI as the virtualization hosting platform for their virtual desktops. The three year cost per server will be about $8800. With an estimated 35 user per server this breaks down to about $250 per user.

The estimated average cost per user is $325 + $480 + $250 = $1055. And this is just the software costs as you will have a significant costs in servers, thin clients and storage.

For a Citrix XenDesktop you will most likely have a Citrix sales engineer working at least one to two weeks and a Citrix sales member having several meetings and presentations to make one sale. Microsoft and VMware would need to work with the customers usually under a volume license agreement to faciliate the purchase of licenses.

So we have Citrix doing most of the work but as you can see they get less than 1/3 of the total software cost.

VMware at 24% ($250 / $1055) gets almost 1/4 of the total software revenue for the least amount of work.
Microsoft at 45% ($480 / $1055) gets the most software revenue for only slightly more work than VMware.
Citrix at $31% ($325 / $1055) gets less than 1/3 of the software revenue but does the most work by far.

These numbers are all estimated based off retail costs. The Microsoft licensing costs could be signficantly lowered if you already have a Microsoft desktop OS installed on the client.

From these numbers we can draw some interesting conclusions.

1. Microsoft benefits greatly from virtual desktops and receives a huge portion of the software revenue.

2. VMware gets about the same amount of revenue ($250 per user) as long as VMware VI is used as the virtualization platform. VMware's desktop virtualization product, View, is about $250 per user for the enterprise version which includes VMware VI.

3. Citrix does most of the work for the sale yet gets less than 1/3 of the total revenue. This is why Citrix needs the base virtualization platform to be Citrix XenServer or even Microsoft Hyper-V. This mostly likely drove Citrix to make XenServer free.

If anyone has questions or more exact numbers please feel free to comment.

Introduction to my VDI blog

This blog focuses on Virtual Desktop Infrastructure (VDI) and related virtualization technologies. I created this blog so I can document and share my experiences and knowledge around virtualization. My last job was at Citrix focuses on developing and evangelizing the desktop virtualization solution by Citrix called XenDesktop. While at Citrix I wanted to blog more about desktop virtualization but I felt I could not be unbiased since I needed to promote Citrix products and technology. So until I find my next job I will be blogging about several virtualization technologies and trends.

I welcome any questions or comments ranging from my job at Citrix to any questions around virtualization.