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Microsoft Application Virtualization 4.6 Read Only Cache for VDI environments #1

July 26, 2010

Introduction and Key Findings

This is the first article of a series discussing Microsoft App-V’s Read Only Cache

Article Series Content

#1 Introduction and Key Findings (this article)

#2 Setting up the Staging Client and Loading Applications into the Staging Cache

#3 Assigning the updated Cache to VDI Virtual Machines


With App-V version 4.6, Microsoft introduced the ability to configure its Client’s Virtual Application Cache (= “Cache”) to be accessed in Read Only Mode (also referred to as “ReadOnlyFSD”).

The App-V Cache is a potentially large file (up to 1 TB max) that contains copies of the application packages (“SFTs”) in order to allow fast (local) access to resources that originally are stored centrally on the network. Due to its purpose, it was designed to reside locally on the App-V Client machine (i.e. a Windows Workstation or a Remote Desktop Server/Terminal Server). Storing the App-V Cache locally on the Client allowed the applications to launch with only a minimum impact to the performance. Because of that “local” design and the requirement to fill (load) new application packages into the Cache, full modification and exclusive access rights had to be given to the Cache File for the App-V core services and drivers in the past.

For VDI environments with hundreds or thousands of Clients, this local and exclusive approach represents a significant cost driver, because in VDI environments usually there aren’t cheap, locally attached Hard Disks installed. Instead, SAN storage has to be bought (or rented) to host the Virtual Machines operating system and applications. Because of the exclusive access approach, each VDI Virtual Machine had to have its own, dedicated App-V Cache, often 4-12 GB in size – although all of these individual cache files potentially contain the same or similar applications.

By introducing the ability to access a shared cache in Read Only Mode, Microsoft allows significant savings related to storage costs compared to old versions of SoftGrid/App-V as well as to other Application Virtualization Solutions. Additionally, it allows to store the App-V Cache file outside the VDI Virtual Hard drive, thus unlinking it from the (virtualized) operating system. This results in an increased flexibility, because changes to the Virtual Application set do not require to modify the VM image any longer.

Because of these potential advantages, the announcement of that Shared Cache approach created certain noise in the App-V community, including some hints of how to create a Shared Cache and fill it with a set of applications.


Posted in App-V, Client
Tags: ,

Freeware Tool to control App-V’s OS values within OSD files

July 22, 2010
1 Comment

During Sequencing, each Microsoft Applicatio Virtualization (App-V) OSD file gets none, one or more entires of Operating Systems that should be capable of running that application (“OS VALUE” tag).

Adding a new OS VALUE tag into already existing OSD files can be done manually, but would be a time consuming process. Also, removing all OS VALUES from the OSDs is time consuming as well.

There is a tool available for a while that is capable of recursively add individual OS VALUES to  OSD files within a specific folder and its subfolders:

But there is a smarter tool available…


Posted in App-V, Tools
Tags: ,
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