Limited Network Performance Preface

One of the big challenges with managed local virtual desktops is the initial  deployment of the OS image. Regardless how such a technology and its management is being designed, there’s no way around getting the basic Image somehow being delivered to the hyper visor. That is specifically painful for remote locations with very limited bandwidth, in case the endpoint can’t be pre-installed and delivered by the IT organization and shipped to the end user.  It’s painful for the end users and stresses their patience to the max. For these poor users being locked to “check-in / check-out” based technology, that’s even the case after the initial deployment… Citrix XenClient and Citrix Syncrhonizer for XenClient was desinged to address these pain points, what ever needs to be transmitted over the wire, will be based on “block level differences” and additionally be compressed befor it’s being sent over the network.

So, how does XenClient overcome the remote VM deployment pain?

With the release of XenClient 2 (Tech Preview as of this writing), Citrix implemented a “Cached Mode”, which allows to send the golden image of a desktop on a optical or USB media using e.g. a courier and during the “download” of the corporate image fromt the backend system, the hypervisor will check the local storage first and if found copy the image locally,  Consequently only configuration, policies and potential differential updates need to be downloaded over the Internet.

The user just connects the USB Stick / Drive to the PC, chooses “Download from Synchronizer” and selects a assigned VM to start the deployment.

What are the prerequisites on the Client side?

By default (Tech Preview of XenClient 2) nothing needs to be done from the XenClient point of view. All required settings in the XenClient db are being set. In case these need to be changed, this will be done by using the “xec” command line tool from the Dom0 (Open a terminal or use ssh if enabled on the XenClient).

The service is called “disksyncmgr” and configuration can be checked / changed as follow:

In case the configuration has to be changed, use the following command against that service:

  • –set enable-dvd-cache true
  • –set enable-dvd-cache false
  • –set enable-usb-cache true
  • –set enable-usb-cache false

How do I get access to the golden image (from the synchronizer)?

The golden images (VHD’s) are stored at the Synchronizer in a compressed format, checksums were calculated during the upload process so just copying a image from a XenClient wont do it….

First you need to find out the location and filename of the VHD files / chain.
There will be a python script you can run on the Syncrhonizer appliance which helps you to locate the data.
(This is not yet the case with the Tech Preview release)

Syntax: python -n name -v version

If I want to get information about my version 2 Win7 image this would be:

Now, the only thing left is to copy the files from the Synchronizer to your USB stick/disk.

Important: The USB disk needs to be NTFS formatted (Optical Media UDF)

One way to copy the files from the Synchronizer is to use scp / ssh, however sshd isn’t configured by default on the Synchronizer. You can learn on how to turn on sopenssh here:

Now, you just drag and drop the required file to your media and you’re set!

Hope this formation help!

Have fun with your XenClient!

Feedback and comments welcome, walter.hofstetter[at]
(P.S. if you need to python script right away, send me a message)