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Top 10 Mistakes Made
10. Not Calculating Network Impact
9. No Profile Strategy
8. Lack of Application Virtualization Strategy
7. Improper Resource Allocation
6. Not Optimizing Antivirus
5. Not Managing Boot Storms
4. Ignoring Virtual Desktops Optimizations
3. Not Enough Cache
2. Default Controller Configuration
1. Improper Storage Design
Page 2 Overview With the excitement and promise of desktop virtualization, many organizations are trying to quickly implement a VDI-type solution to realize the expected benefits. Unfortunately, this exuberance has resulted in some implementation issues due to improper planning and design. This white paper focuses on the top 10 mistakes made, identified by Citrix Consulting, when implementing a desktop virtualization solution.
10. Not Calculating Network Impact Regardless of the flavor of virtual desktop being implemented (hosted shared, hosted VM-based VDI, local streamed, etc), the network plays a critical role. The user experience degrades as the latency increases and the bandwidth decreases. Proper network planning must be based on the type of work users are performing and the overall network topology. Many organizations estimate 20 Kbps per user, as this was used for XenApp hosted applications. However, virtual desktops require
more bandwidth because:
In default configuration, virtual desktops provide a greater and richer experience than the default XenApp configuration.
Virtual desktop users are idle less often than hosted application users. For example, if a user is sitting in front of a workstation and is accessing a hosted application on XenApp, the desktop and XenApp applications both appear as active. However, when the user is not working with the XenApp application, they are identified as idle by XenApp even though they might be active on their desktop. Due to this difference, the desktop will have less idle time than XenApp hosted applications.
Desktops access and consume more multimedia and graphical mediums than most applications. A user’s desktop session also includes internet activity, which often includes more graphics, video and sounds. When using a XenApp hosted application, these multimedia activities are only utilized if the application allows.
Estimating network impact is not a trivial matter because the ICA/HDX protocol tunes itself based on the amount of bandwidth available. The less bandwidth available means more compression is applied. Also, any estimate must include percentages for different user activities: typing, graphics, Internet, video (Flash, WMV, etc), and printing. With this information, the following can be used to
create an ESTIMATE:
By calculating the percentage of time a user is expected to be doing certain activities, a rough estimate can be determined for ICA bandwidth requirements. If multiple users are expected to be accessing the same type of content (videos, web pages, documents, etc), integrating the Branch Repeater into the architecture can drastically reduce the amount of bandwidth consumed. However, the amount of benefit is based on the level of repetition between users.
Additional details on the bandwidth estimates can be gathered by referring to the following Citrix white paper: CTX124457 - Performance Assessment and Bandwidth Analysis for Delivering XenDesktop to Branch Offices.
9. No Profile Strategy The user’s profile is one of the major ways the pooled virtual desktop becomes personalized. If users are going to accept a new desktop strategy, they must have the ability to personalize their desktop environment. The personalization must not negatively impact the performance of the environment.
When organizations do not properly plan the profile strategy, one or more of the following will
Slow logon/logoff performance Inconsistent results
These challenges will result in a negative perspective of the entire solution. As an example:
An organization had a profile strategy in place. Users started working in the new system. One day, a user had a profile corruption issue which resulted in the deletion of their entire profile. This meant the user had to recreate their entire personalized environment. After the profile was deleted, the user also quickly noticed all of their documents were deleted. Upon closer inspection, the user stored their documents in the “My Documents” folder. When the profile was deleted, the My Documents folder was also deleted.
To overcome these potential challenges, a profile strategy must be put into place that includes items
Folder Redirection: Have portions of the profile stored on a network drive outside of the roaming profile. This allows the profile to load faster and protects these items from profile deletion.
Group Policies: Utilize group policies to configure the user’s virtual desktop profile. These policies should only be used when the user logs onto a virtual desktop.
Persistence: Utilize a profile solution that allows for the extraction and storage of the personalized components of a user’s environment outside of the profile.
Additional profile strategy recommendations can be found in the following the following article:
CTX124799 User Profiles for XenApp and XenDesktop
8. Lack of Application Virtualization Strategy Desktop virtualization can be successful without an application virtualization strategy, but only in certain situations, and typically only in smaller, less complex environments. One of the primary goals of desktop virtualization is to simplify the management of the desktop environment. One way of accomplishing this goal is to reduce the number of images. However, the primary factor that often dictates the need for additional desktop images are application sets.
Organizations typically deal with this challenge in one of three ways:
1. Installing every application into a standard desktop image
2. Creating multiple images with different application sets based on different user groups
3. Removing the applications from the desktop image and delivering via application virtualization All three of these options are valid and work in different scenarios. However, applying one of these options to the wrong environment will result in major challenges as the following examples demonstrate.
One organization installed all of their business applications within a single desktop image.
After the image was created and tested, it worked fairly well until certain applications required updates. Those updates sometimes caused issues with the other applications that did not appear until the image was fully deployed. Users also started to express confusion why they could see all of the applications but were unsure what they were supposed to do
In another example, an organization tried to over design a virtual desktop solution by doing the
A small organization consisting of 200 users implemented a virtual desktop solution.
Following the complete virtualization guidelines, the organization virtualized all of the applications via hosting and streaming technologies. Although the solution functioned for the users and integrated seamlessly, trying to maintain the different components became a struggle. As the organization only had 4 different application sets, it would have been easier to implement 4 desktop images instead of a complete application virtualization solution.
A proper application virtualization strategy must determine
1. If the number of desktop images is too great to manage effectively. As the number of images increase, the environment becomes more difficult to maintain. By virtualizing the applications, the number of images can be reduced significantly. If, on the other hand, only a few images are required, the time and effort to support an application virtualization solution outweighs the benefit.
2. If traditional (non-virtualized) desktops are still required within the organization. If the applications are virtualized, the traditional desktop management is simplified as these devices can utilize the virtualized applications.
3. If hosted applications are required or if all applications can be streamed to the desktop. By removing the hosted application component, the application virtualization aspect of the environment is simplified as fewer resources are required.
In many implementations, application virtualization is a necessity. Integrating those applications into the virtual desktop must also be done correctly. As a general recommendation, applications
should be integrated into a virtual desktop as follows:
6. Not Optimizing Antivirus Antivirus solutions are important, even in a virtual desktop environment. If using hosted shared desktops or hosted VM-based VDI desktops, those virtual desktops are located within the data center with other critical systems. If a virus made it into the data center, the environment is at serious risk. However, simply adding an antivirus solution to the virtual desktop can have a major impact on the virtualization infrastructure, and even cause users to experience poor virtual desktop performance.
If the virtual desktops are streamed with Provisioning services, and those desktops start a full system scan at roughly the same time, those virtual desktops will eventually request the entire vDisk image.
This not only overwhelms the network and Provisioning services, but also impacts the storage infrastructure as the write cache is utilized. Overcoming these issues is a fairly easy matter and is
based on the following recommendations:
1. The vDisk image must be free from viruses. It is recommended to do a full system scan in private image (read/write) mode. This guarantees the image is clean.
2. When the vDisk image is in standard mode (read-only), the antivirus should be configured as
3. Reconfigure antivirus so that the virus definitions file is stored on a persistent disk so antivirus doesn’t have to download the entire definition file on each startup.
5. Not Managing Boot Storms Most organizations have users arriving and logging into their desktops at roughly the same time. It is recommended to use the XenDesktop workstation group idle settings to prepare the environment for the user logon storm by booting desktops so many minutes before the users arrive. This makes the desktops immediately available for users and allows the system to recover from the massive boot storm. However, when the workstation group’s defined boot time is reached, the controller might try to start thousands of virtual desktops simultaneously.
A virtual desktop startup has the single largest impact to any virtual desktop implementation. The XenDesktop controller must tell the hypervisor to start a new desktop and the hypervisor must allocate resources. Sending too many requests to the hypervisor can overwhelm the hypervisor’s management layer (VMware ESX, Microsoft Hyper-V and Citrix XenServer). This should be mitigated by configuring the maximum number of simultaneous startups the controller can request.
This is done by doing the following:
On the XenDesktop Master Controller, edit the file: C:\Program Files\Citrix\VmManagement\CdsPoolMgr.exe.config Locate the MaximumTransitionRate entry and use a value of 20 (change based on actual environment parameters). The value entered forces the XenDesktop controller to limit the number of requests that are sent to the hypervisor’s management layer.
This setting should be made to all XenDesktop controllers in the event the master fails and a backup takes over.
4. Ignoring Virtual Desktops Optimizations Organizations often spend time to create a customized standard operating environment for their desktop operating systems. This often involves specific location settings, default application settings, and desktop descriptions. However, when delivering an operating system into a virtual desktop, many organizations do not go far enough to optimize the desktop for the virtualized environment. Whether the desktop is a hosted VM-based VDI desktop, a local streamed desktop or a hosted shared desktop, certain optimizations allow the hardware to focus on user-related tasks as opposed to extraneous system-related tasks. The following are examples of virtual desktop
Disable Screen Saver: Utilizing a graphical screen saver consumes precious memory and CPU cycles when the user is not even using the desktop. Those processes should be freed and used by other users. If screen savers are required for security purposes, then simply blanking the screen should be invoked as this does not impact the memory and CPU consumption.
Disable Unneeded Features: Windows 7 contains many valuable components like Media Center, Windows DVD Maker, Tablet PC Components, and Games. These applications are memory, CPU and graphics intensive and are often not required in most organizations. If these components are made available to users, they will be used. It is advisable to remove unneeded services before deploying the first images.
These are only a few recommendations, but it is obvious that optimizations have a major impact on the virtual desktop environment.
Note: The virtual desktop optimization best practices for Windows XP is located in CTX124239