What is VDI?

Updated on January 15, 2007. Updates in red. 

Virtual Desktop Infrastructure (VDI) is not a product. You can't call up a company and ask for 5 licenses of VDI.  It is concept comprised of multiple solutions or products to achieve a Virtual Desktop Infrastructure (though recent announcements have Citrix XenDesktop as a single product that comes very close). The concept of VDI virtualizes desktops operating systems (Vista, XP, Linux, etc) and deliver the remote view of the desktop via a display protocol. In addition, there will be management and control systems to manage the provisioning/deprovisioning of virtual machines and applications.

By bringing the desktop from under the client desk into your data center, your administrative costs can decrease for desktop support. Now that the desktop is in the data center, you can backup the desktop and provide increased performance for users even though they are remote and on slow connections. You can share the same desktop amongst multiple users. It can be remotely accessible from anywhere. 

 

What actually makes up a VDI solution?

So Virtual Desktop Infrastructure consists of a few major parts:

• Remote Display - A device to display the connection
• Application Delivery System - Technology to deploy and update applications within the desktop
• Connection Broker - A broker that provides the remote display protocol, possibly provides remote access, possibly access to local devices.
• Virtual Machine Management - Manages the provisioning/deprovisioning of private or shared virtual machines.
• Operating System Virtualization - Virtualized operating system layer to provide multiple virtual machines on the same physical hardware.
  

What's all the hype?

There are a lot of desktops in this world of ours. Imagine if every desktop became a virtual machine. You organization may average 20-100 employees for every 1 server, but your probably average 1 employee to 1-2 desktops. How many licenses of "Operating System Virtualization" solution would need to be purchased? That is why you have so much push for this. But there are costs associated with implementing VDI that are not readily discussed and are sometimes downright misleading.

There are costs that must reviewed to determine it really is going to save money.

• Conceptually VDI takes low cost PCs ($500-$1000) on local cheap desk storage under cheap office space (sitting under a desk). Now you will be taking that, and putting it on high end hardware with high end storage in what is the most costly space, your data center.
• Also you still need a desktop to connect to the environment, whether this is an existing desktop or replacing the existing desktops with Windows/Linux Based Terminals.
• Licensing of Anti-Virus software, Monitoring software, Backup software, etc will still need to be purchased for each desktop OS.
• If you currently don't have any SAN solution or are low on capacity, there will be costs associated to implement or expand.
• Proper sizing of the environment (How much disk, memory and CPU is required to support a single user?). Example: Microsoft Vista requires 15GB of disk, and 1GB of RAM, but highly suggests 40GB of disk and 2GB of RAM.

Here are some quick

• Is it economical to buy a high end server with maxed out memory to get 15-50 virtual desktops?
• What other solutions must be acquired to deliver and manage the desktop?
• How do you push applications and upgrades?
• How do you control who has access to what applications?
• How do you give administrator and control access to other devices and peripherals (USB drives, CD-ROMs, webcams, digital cameras, blackberry/cell phone synchronizers, scanners, printers, etc).
• Will you backup desktops and do you have enough disk/tape to perform this action?

 

What is the current state of VDI?

Since there is no single solution at this time (though companies will tell you otherwise right now), it is a concept in flux.  Companies are coming out with solutions or have solutions on their roadmaps to deliver each of the major components. Since Jan. 07, Citrix and VMware (leaders in this space) have made acquisitions to provide the end-to-end solution for VDI.

 

 

Why are Citrix and VMware the leaders for VDI?

Though there are other companies trying to vie for a piece of the VDI pie, these two companies have proven themselves to be the leaders in this space, albeit from slightly different angles.

Citrix has been delivering applications and desktops via a Server Based Computing model since 1989. Their ICA protocol and Presentation Server (Formely MetaFrame) product line have powered much of the Fortune 500 down to small 2 person companies.  By delivering applications over low bandwidths and simplifying the maintenance (one install of an application can support 100s of users), they are the leader in application delivery/virtualization. 

VMware, founded in 1998, has emerged as the leader in the server and desktop virtualization market. Their enterprise class solution provides a robust and stable solution to support multiple operating systems on the same physical hardware. These "virtual machines" are hardware independent and self contained systems that can be easily migrated to new hardware, or for disaster recovery.

So these two companies started at different ends of the spectrum. Citrix virtualizing applications. VMware virtualizing operating systems. Each doing their own thing and doing it the best.

In the Beginning

At first, these two companies played well with each other. Citrix was working hard to optimize itself with VMware and VMware was hard at work to deliver best practices around virtualizing Citrix.  They were not really competing in the same space and both had great client loyalty. 

The First Blow

In my opinion, the first real blow came when VMware tried to push VMware ACE as a remote access solution.  It really made no sense. Sure you no longer had to support the laptop/desktop running ACE, but suddenly you had a full OS with applications to deal with. It's hard enough patching operating systems and applications internally, but now you have to do it on a PC that only connects once per month and now the "updates" are GBs of data (not just MBs of data). Citrix was slighted since they were the "access company" (marketing slogan at the time).

They Play Nice

Then in 2006, VMware really started pushing clients to implement VDI. They didn't really tell them it wasn't a product, but they started pushing.  The VMworld 2006 Exhibit Hall was full of connection broker companies claiming to manage the connection. Some provided new remote display protocols, some had VPN-like access, and some integrated with VMware VirtualCenter. VMware had stated they would not get into the connection broker market since they had great partners to develop this technology.  We've heard that from Microsoft (and others) right before they bought a company. Citrix was there (all the way in the back). But it made sense, best of breed remote display (Citrix) with best of breed (VMware).  (Note: Let's be honest Microsoft RDP is decent, but not enough support for local devices and is pain to manage since most of the management is controlled by the client side.)

Citrix Goes on the Offensive

In early 2007, Citrix acquired Ardence to stream the entire operating system to a machine with out using any disk space (recently renamed to Citrix Provisioning Server). So you could use 0 disk space on the client PC and still deploy Windows XP or even Windows 2003 Servers. While this was not a direct competitor to virtualization, it was discussed as an alternative to virtualization since you received some of the benefits (dynamically add/remove capacity, OS is no longer locally managed, static OS configuration like a non-persistent disk), but still had the full capacity of a physical server.  Interesting technology and was very slick, but as a real world application, only made sense for a select type of organizations that could also deal with Provisioning Server's downfalls (Provisioning Server's best ROI was in read-only disks, so no changes could be maintained).

VMware Strikes Back

Then it happened in May of 2007, VMware bought a connection broker (Propero) and put Virtual Desktop Manager on its roadmap (currently in Beta). This was the exact opposite of what the stated months earlier.

Citrix Counters

Even though Citrix's Desktop Broker (free) and Desktop Server 1.0 (gotta buy it) were average at best, everyone thinks the ICA protocol (Used by Citrix products to perform the remote display of an application or desktop) to the desktop is the holy grail. All the features Citrix has been doing for years on a server (client redirection, bidirectional audio, local device support, universal print driver) would give Citrix a huge advantage along with their current integration of Presentation Server in most organizations. Connect the user to the best method of application delivery. Put the user on Citrix Presentation Server for large corporate applications with security and administrative control, but deliver them a virtual desktop when they need a customizable environment that the user controls. When VMware announced they were not going to be in the connection broker market, and then bought Propero, the gloves came off.

Citrix buys XenSource to deliver virtualized desktops (and servers).  That was a pretty big shock since the channel was still able to say they didn't compete up to that point. But with this purchase, Citrix let it be known that they want a part of the OS Virtualization market.

The future is not certain

There may be other factors also driving this, but since I don't work for either company... this is just an external view of what seems to be occurring. Will VMware buy an application delivery company to push apps into their VMs? Will Citrix buy another company to improve XenSource high-availability and make it more enterprise class? Will any of the Connection Brokers be able to fully deliver a rich desktop equivalent environment with audio and video (Citrix has been doing it for years, and they are not perfect)? What your organization really save money on delivering desktops like this? When will the solution be fully baked by each company? Will RDP (even if improved) provide the performance required? Will VMware buy an Application Delivery/Deployment solution?

VMware acquires Thinstall
In January 2008, VMware acquired Thinstall to package an application into a single executable for distribution. This now gives VMware a method to deploy an application into their Virtual Desktops (or even for non-virtualized desktops). There are some questions as to how this method of application delivery will work for applications that must communicate (think how outlook.exe calls winword.exe to compose an e-mail or open a word document. Does that mean Winword.exe has to be packages with Outlook? What about Adobe Acrobat Reader, Excel, Powerpoint, etc? Of course, the virtualized application will be able to interact with locally installed applications, but can it communicate with other Virtualized applications? It would have made a lot of sense for VMware to buy Provison Networks, but Quest software snagged them up.  Interesting acquisition, but as I've already stated... The picture is not done being painted.

What are the Pros and Cons of a Pure Citrix VDI Deployment?

 

• Remote Display - Citrix has wide acceptance in its remote display protocol (Windows based terminals, Linux, All Windows OS including CE, Mac client, Java client etc).
• Application Delivery System - Citrix can deliver an application in multiple methods. Streamed to the desktop (whether the desktop is physical or virtual) or virtualized via Presentation Server. This flexibility allows administrative control as to how business applications are delivered. (more complex applications may be virtualized and simpler applications or offline applications can be streamed to the user).
• Connection Broker - Although the marketing machine of Citrix has a good message, "Deliver the application in the most appropriate method for the user", the technology isn't baked yet. As of today, you have to RDP to the desktops so you do not get the full capabilities of the ICA protocol. Change is immanent here. Desktop Connector will be able to deliver ICA directly to the desktop. In addition, integration with Citrix's existing VPN solution and the ability to deliver best fit desktops for users make Citrix a formidable presence in the market.
• Virtual Machine Management - Citrix has Desktop Connector on the roadmap to manage the virtual infrastructure. Also, Citrix is developing this solution and promoting Citrix Provisioning Server (formely Ardence) as its management component. Citrix Provisioning Server streams the entire OS into the desktop. Citrix Provisioning Server has two methods to stream an operating system: shared or private. Private is probably the best ROI, but shared is probably what most users will demand.
• Operating System Virtualization - Citrix's acquisition of XenSource allows them to now virtualize servers and desktops. Though this solution is not as robust as VMware, its lower price point may be enticing to clients. The XenDesktop solution will force you to use XenServer as the OS Virtualization platform.

Citrix has two types of deployment.

VDI with Citrix Presentation Server

VDI without Citrix Presentation Server

Citrix XenDesktop to virtualize desktop operating systems, broker the connection and deliver the best fit desktop for a user and finally to stream a static or changeable operating system. Citrix Presentation Server to virtualize applications. Citrix Access Gateway for Remote Access/VPN* Citrix Password Manager for Single Sign-On Solution for applications* Citrix EdgeSight to monitor application performance*

Citrix XenDesktop to virtualize desktop operating systems, broker the connection and deliver the best fit desktop for a user and finally to stream a static or changeable operating system. Citrix Access Gateway for Remote Access/VPN* Citrix Password Manager for Single Sign-On Solution* Citrix EdgeSight to monitor application performance*

* These products are not required, but they do provide a more efficient full featured environment for end users and administrators.

Citrix Pros and Cons

Pros

Cons

Citrix is currently the closest at being an end to end solution for VDI. Citrix has the best protocol (ICA) for delivering a rich desktop environment for users. Citrix has the most local client device support in the ICA protocol Citrix has been using and improving its Universal Print Driver technology for over 5 years. Citrix has been delivering remote access solutions since its inception. Citrix Provisioning Server to stream a static or changeable operating system to decrease disk space requirements. Multiple methods to deliver an application: stream to virtual desktop, stream to desktop, or virtualized on Presentation Server. Citrix XenServer provides many of same features and great performance at a much lower price point.

Citrix just entered the OS virtualization market. Citrix's Connection Broker is currently lackluster at best. A lot of work is needed, but the roadmap looks promising for Q1/Q2 of 2008. Citrix Provisioning Server has a great ROI for private/read-only OS streams, but that may not be what users want for their environment. Citrix is looked at as a late entrant into this market and VMware Sales/Marketing is well ahead of them at this point.

 

 

 

What are the Pros and Cons of a Pure VMware VDI Deployment?

• Remote Display - VMware is using the Microsoft RDP protocol (Used in Terminal Services implementations) to deliver its remote display. Clients exist and can be used must operating systems, but it is not as optimized as the Citrix ICA protocol when it comes to a rich display (IE, video, audio, flash, etc). VMware may provide and enhanced RDP or create their own, but then they will need to get the client portion of the display protocol on devices. And that can take some time.
• Application Delivery System - Prior to VMware's recent Thinstall acquisition, they didn't have a solution in this space and were relying on 3rd party companies to deliver the application the desktop. Now with ThinStall technology, applications can be packaged and simplied copied as one executable to the desktop. Other 3rd party technologies(e.g. Citrix Presentation Server (virtualize or stream), Microsoft SMS or SoftGrid) can still be used and VMware is not forcing anyone to use Thinstall (unlike what Citrix is doing with forcing everyone to XenServer to use XenDesktop).
• Connection Broker - VMware acquired Propero earlier this year and has a product in beta (Virtual Desktop Manager).
• Virtual Machine Management - Virtual Desktop Manager is currently in beta to manage the Virtual Machines provisioning/deprovisioning capabilities.
• Operating System Virtualization - VMware is the market leader in OS virtualization and provides enterprise class solutions for high availability and performance.

A typical VMware deployment has the following.

VDI with VMware

VMware ESX Server for Operating System Virtualization VMware Virtual Desktop Manager as a Connection Broker, Remote Access Solution, and provisioning. VMware Virtual Center for management and alerting

 

 

Pros

Cons

VMware has the most widely used OS virtualization technology. VMware is looked at as the leader in VDI technology. VMware ESX features are more enterprise ready. VMware ESX Server has such a great install base, it may become the de facto OS virtualization technology for clients who already it in place. Thinstall technology can be used to package applications into executables that can simply be copied to the desktop.

VMware's solution is not end to end. VMware's connection is based on Microsoft RDP which isn't as full featured as the Citrix ICA protocol. If VMware enhances or replaces RDP in their solution, the client availability on existing devices will decrease. Additional solutions will need to be acquired to install/manage applications within the desktop. VMware's VPN/Reverse Proxy component in the connection broker can be complex and not widely compatible. (Example: It does not appear to support a Mac OS X client). Clients may not want to pay for enterprise OS virtualization features for desktops.

 

Which solution VDI is best?

There is no right answer for everyone. It comes down to requirements gathering and a full fledged proof of concept. There is no other way to do this. Each company will say they can solve everything, but they can't right now. As you can see from the rest of this article, there are a lot of information that need to be gathered about your environment and how your users use VDI.  Based on that information a proper gamelan can be laid out for short term and long terms goals. Some clients may chose to use all Citrix or all VMware or a combination, based on the requirements. Some may use all of one company's solution now, and then switch in 1 year as more advances are made in this concept.

 

How do Citrix XenServer (part of XenDesktop solution) and VMware Virtual Infrastructure compare?

 

Features/Design	Citrix XenServer 4	VMware Virtual Infrastructure 3
List Pricing All Licensing is per 2-CPU Sockets	Standard Edition - $750 + $150 for Base Support 1 Yr. Enterprise Edition - $2495 + $500 for Base Support 1 Yr.   Renewal Support per year is $500. https://xensource.ltg.info/xenshop/productselection.aspx   Note: Pricing may change due to acquisition and marketing. Price listed above is for Base Support only. No management License Fee	Virtual Infrastructure Foundation - $995 Virtual Infrastructure Standard - $2995 Virtual Infrastructure Enterprise - $5750 VirtualCenter - $4995   Support - 10%-20% additional cost for support on all products per year. http://vmware.com/products/vi/packaging.html Note: VirtualCenter is required for many of the Standard and Enterprise features, and is recommended to be purchased per data center or environment  (e.g. More than 2000 Virtual Machines or more than 200 hosts)
Virtualization Model	Para-Virtualization - OS in Virtual Machine knows it is virtualized and has modified its code to optimally perform allowing for direct hardware communication resulting in less overhead. Even though the major OS manufacturers support this model, XenSource supports a smaller number of Operating Systems at this time.	Virtualization - OS in Virtual Machine does not know it is has been virtualized allowing for a larger number of OSes to be virtualized.   Support for Para-virtualization guest OSes in a future release.
Migration of Online VMs	Yes. New in 4.0	Yes since 2.0.
High Availability	No (requires 3rd Party)	Yes since 3.0
Dynamic Load Balancing	No	Yes since 3.0
Host Resource Cluster	Yes (16 hosts maximum)	Yes (16 hosts maximum for HA, 32 hosts maximum for DRS)
Configurable Resource Pooling	No. Note: A Resource Pool in XenSource is a cluster of hosts servers for management purposes.	Yes
On Start Load Balancing	Yes	Yes, with DRS enabled to "Partial" or "Fully Automatic"
Offloaded Virtual Machine Backup	No	VMware Consolidated Backup offloads backups from the host servers. Script based or 3rd party integrated.
64-Bit Support	True 64-bit support	Emulated 64-bit support
VLAN Support	Yes	Yes
Hardware Virtualization Support	Supported and recommended for para-virtualization	Supported but not recommended to be enabled as VMware states their code is more efficient than the Hardware Virtualization.
Management	Built-In at no additional cost, not a single point of failure. No additional requirements.	Additional $4995 + Support and Maintenance for VMware VirtualCenter. Recommended 1 per data center. If not built correctly, can be a single point of failure. Requires database and license server.
Online Snapshot	Yes	Yes
Limits	128GB of RAM on Physical Host 32GB of RAM per VM 8 CPUs per VM	64GB of RAM on Physical Host (VI 3.0) 128GBof RAM on Physical Host (VI 3.5) 16GB of RAM per VM (VI 3.0) (32GB of RAM per VM (VI 3.5) 4 CPUs per VM
Hardware	Limited to HW with a CPU that supports Hardware Virtualization	Limited to HW supported by VMware
Other Features	Roadmap has not been made public	Site Recovery Manager (To be released later this year) Update Manager (VI 3.5 with Virtual Center 2.5) Storage VMotion (VI 3.5 with Virtual Center 2.5) Continuous Availability (roadmap future release)

 

Reference Documents

VMware Virtual Desktop Manager
http://www.vmware.com/pdf/datasheet_vdm.pdf/pdf/datasheet_vdm.pdf 

VMware VDI Overview
http://vmware.com/products/vdi/

Citrix Application Delivery Infrastructure
http://www.citrix.com/lang/English/ps2/technology/index.asp

Citrix XenDesktop
http://www.citrix.com/English/ps2/products/product.asp?contentID=163057&ntref=hp_nav_US  

Citrix XenServer (Marketing & Training Material)

VMware Virtual Infrastructure (Marketing & Training Material)

Configuration Maximums for VMware Infrastructure 3
http://www.vmware.com/pdf/vi3_301_201_config_max.pdf