MED-V Trim Transfer Technology

Applies To: Microsoft Enterprise Desktop Virtualization

A newer version of the Microsoft Enterprise Desktop Virtualization (MED-V) documentation library is now available. To view the most recent MED-V documentation library, see https://go.microsoft.com/fwlink/?LinkID=167079.

The MED-V advanced Trim Transfer de-duplication technology accelerates the download of initial and updated virtual machine images over the LAN or WAN, thereby reducing the network bandwidth needed to transport a MED-V workspace virtual machine to multiple end users.

This breakthrough technology uses existing local data to build the virtual machine image, leveraging the fact that in many cases, much of the virtual machine (for example, system and application files) already exists on the end user's disk. For example, if a virtual machine containing Windows XP is delivered to a client running a local copy of Windows XP, MED-V will automatically remove the redundant Windows XP elements from the transfer. To ensure a valid and functional workspace, the MED-V client cryptographically verifies the integrity of local data before it is utilized, guaranteeing that the local blocks of data are absolutely bit-by-bit identical to those in the desired virtual machine image. Blocks that do not match are not used.

The process is bandwidth-efficient and transparent, and transfers run in the background, utilizing unused network and CPU resources.

When updating to a new image version (for example, when administrators want to distribute a new application or update), only the elements that have changed ("deltas") are downloaded, and not the entire virtual machine, significantly reducing the required network bandwidth and delivery time.

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You can configure which folders are indexed on the host as part of the Trim Transfer protocol, based on the host operating system. These settings are configured in the ClientSettings.xml file, which can be found in the Servers\Configuration Server\ folder.

When applying new settings, the service must be restarted.

<HostIndexingXP type="System.String[]"> 
- <ArrayOfString>
<string>%WINDIR%</string> 
<string>%ProgramFiles%\Common Files</string> 
<string>%ProgramFiles%\Internet Explorer</string> 
<string>%ProgramFiles%\MED-V</string> 
<string>%ProgramFiles%\Microsoft Office</string> 
<string>%ProgramFiles%\Windows NT</string> 
<string>%ProgramFiles%\Messenger</string> 
<string>%ProgramFiles%\Adobe</string> 
<string>%ProgramFiles%\Outlook Express</string> 
</ArrayOfString> 
</HostIndexingXP> 
- <HostIndexingVista type="System.String[]"> 
- <ArrayOfString> 
<string>%WINDIR%\MSAgent</string> 
<string>%WINDIR%\winsxs</string> 
<string>%WINDIR%\system</string> 
<string>%WINDIR%\system32</string> 
<string>%WINDIR%\Microsoft.NET</string> 
<string>%WINDIR%\SoftwareDistribution</string> 
<string>%WINDIR%\L2Schemas</string> 
<string>%WINDIR%\Cursors</string> 
<string>%WINDIR%\Boot</string> 
<string>%WINDIR%\Help</string> 
<string>%WINDIR%\assembly</string> 
<string>%WINDIR%\inf</string> 
<string>%WINDIR%\fonts</string> 
<string>%WINDIR%\Installer</string> 
<string>%WINDIR%\IME</string> 
<string>%WINDIR%\Resources</string> 
<string>%WINDIR%\servicing</string> 
<string>%ProgramFiles%\MED-V</string> 
<string>%ProgramFiles%\Microsoft Office</string> 
</ArrayOfString> 
</HostIndexingVista>