Welcome to another vWorkspace 7.1 Feature Spotlight. Today we will be talking about a new feature that supports the management of differencing disks from the vWorkspace console against Hyper-V and SCVMM 2008 R2.

A differencing disk is a virtual hard disk you use to isolate changes to a virtual hard disk or the guest operating system by storing them on a separate file. They are very similar to the Undo Disk feature from Virtual PC days. Where Undo disks could have multiple stages, differencing disks are associated with only one VHD file that is sometimes called a child VHD.

Using differencing disks is an excellent way to save on storage since the size of the Hyper-V child VHD file after creation and sysprep is usually about 500-600mb and then will grow over time. Using technologies like folder redirection, user profile management, APP-V 4.6 with its new shared cache functionality and also de-dupe functionality that might be available from your storage vendor will further reduce the amount of space you need to house these images.

Bringing the differencing disk technology to vWorkspace provides a way to batch create any number of virtual machines and automatically add them to a computer group and then be managing them from a single delegated user interface.

Once we know how many virtual machines to create (first screenshot) we are then presented with the option to choose Standard (full clone) or Rapid Provisioning (Differencing Disk).

The above screenshot allows you to choose which parent virtual hard disk you will use for the provision. During Rapid Provisioning vWorkspace will ask you to choose the template from VMM if none are already listed. We then copy the VHD over to the CSV/Drive of your choice, mark it as read-only and then rename the file with a timestamp. This allows vWorkspace to track the virtual machines that have been created using a given version of the parent disk. If you try to delete a parent and there are associated child VHD files you are presented with a warning message.' Losing access to the parent VHD is catastrophic to child VHD images.

Naming and mask are presented next. This allows you to set the hostname and use a wildcard for vWorkspace to create hostnames and then increment then accordingly.

With the naming taken care of and parent VHD chosen you are asked where to create the child VHD images. You have the option of creating the images on a single CSV/drive or spreading the creation of them across some/all to balance disk I/O.

With image type, naming and locations set you then need to choose your sysprep options.' If you choose Do not specify sysprep customizations vWorkspace will use any Hardware and Operating System profiles associated with the VHD from SCVMM.

Choosing the Specify sysprep options presents a dialog box with the option to import pre-built unattend.xml or sysprep.inf files or you can choose to use the vWorkspace sysprep wizard and answer some basic questions like OS, Time zone, Product Key, Domain Join info and even OU location and initial firewall settings. These will then be used every time you provision more virtual machines or do a reprovision.

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As we near the end of the wizard you are asked if you want this provision request to happen now or to schedule for creation at a later time.' Once created you also can have this happen on a continual basis.' Maybe spinning up virtual machines every Sunday night to prepare for a training session or new hires.

This screen is your last chance to back out...' Once clicked the provision request is sent to SCVMM and the machines created.' Average virtual machine creation varies based on resources.' We have seen creation time anywhere from 4m to 8m and this is run in parallel (default is 5 at a time) and can be moved up or down based on your hardware and needs. Initial child VHD size is usually in the 500-550mb and then grows based on what you then install into each virtual machine. This is where using technologies like App-V 4.6 shared cache, folder redirection and profile management as well as utilizing disk dedupe technologies comes in handy to keep your child VHD images small.

If you choose to use differencing disks you will inevitably run into the need to update the gold or master image with a service pack or hot-fix. You then will need a way to update the running virtual machines in your pool. vWorkspace allows for you to reprovision the entire pool or selected virtual machines from our UI using either the existing master or pointing to an entirely new master image. This can also be configured to run on a schedule or even to reprovision virtual machines after a user logs off their session.

I hope this was informative and provided a good walkthrough of the differencing disk functionality provided by vWorkspace.

Here's a look at a full-motion video demonstration of' Rapid Virtual Desktop Provisioning for Hyper-V / SCVMM: