Microsoft Application Virtualization (MS App-V) platform allows applications to be deployed in real-time to any client from a virtual application server. It removes the need for local installation of the applications. Instead, only the App-V client needs to be installed on the client machines. All application data is permanently stored on the virtual application server. Whichever software is needed is either streamed or locally cached from the application server on demand and run locally. App-V applications are also sandboxed from each other, so that different versions of the same application can be run under App-V concurrently
MS App-V thus allows centralized installation and management of deployed applications. It supports policy based access control; administrators can define and restrict access to the applications by certain users by defining policies governing the usage. The App-V client presents the user with a list of applications, to which the user has access. The user can then launch a virtualized instance of the application. Depending on the configuration, the systems administrator can be either notified of the action via email or it can require an explicit confirmation from the administrator for the application to start streaming and initialize or it can just simply check the Active Directory for the user's rights and stream the application to the user if it is authorized to run the application. The App-V client can also install local shortcuts that bootstrap the process of launching individual virtualized software instances.
Architecture
lthough App-V is best known for being deployed using the dedicated App-V Management infrastructure, these days Microsoft offers three deployment options. These three options are significantly different from an architectural standpoint: Dedicated App-V Management Server, Shared System Center Configuration Manager Architecture, and "Stand-alone" Mode wherein the application may be delivered manually.
App-V Application Virtualization is composed mainly of two components – SystemGuard and App-V Sequencer. SystemGuard tracks and analysis configuration repositories and resources used by the application and intercepts the use of these resources, redirecting them to the virtualized instances of the resources. Virtualized resources include virtualized data such as user profile information and data; virtualized system services, such as COM controls, windows services and copy/paste abilities; and virtualized configuration repositories like registry hives and INI files
App-V sequencer is the component which packages an application for virtualization and streaming. It also packages specific DLL files that it might require at the client side. It then packs all the application code and data into App-V's proprietary format that makes it more suitable for streaming
At the client, when a streaming request is made to an App-V server, portions of the entire sequencer package are transferred to the client, who unpacks and initializes the SystemGuard environment and hosts the application inside it (with System Center Configuration Manager and the stand-alone client, the entire package contents are transferred). Each package is cached by the client for the duration of the application session. User settings are stored in the local system itself.
Virtualized application packages can also locally reside at the client computer, thus eliminating the need of application server and streaming. Microsoft Systems Management Server can be used to push these packages to the client computer in the absence of a virtual application server. In this scenario, the App-V SMS Connector can be used to locally manage the application packages.
Limitations
- Microsoft Office plug-ins: Although one can sequence Microsoft Office plug-ins, it is not advised to sequence them due to many technical & usage issues. For example, in a situation where there are more than two plug-ins used by a user, if they are sequenced separately, then the user does not have control over which plug-in sequence starts when he opens a document. The only work around to resolve the issue is by creating a single suite or dynamic suite of all the plug-ins.
- Application Size: If the maximum client cache size is set to at least 4 GB (The max can be 64 GB), then the maximum size of application (sft file) which can be streamed on that machine is 4 GB. All applications that have an installed footprint greater than or equal to the max client size, set by the client, should not be sequenced. The maximum application size Softgrid can handle is 4GB, due to the use of the FAT32 file-system.[5]
- Device Driver: App-V presently does not support sequencing of kernel-mode device drivers; thus any application that installs a device driver cannot be sequenced. The only exception to this is when the device driver can be pre-installed locally; in this case, the application is sequenced without the device driver.
- Auto Update: Applications with automatic updates should not be sequenced if their update mechanism cannot be disabled. Sequenced applications usually fail to update. In addition, allowing auto-update leads to non compliance of application version.
- Services: Services can be started when an application starts and shuts down or when an application main executable terminates. Only user-mode services are suitable candidates for sequencing.
- COM+: Some applications which use COM+ might not work properly in a virtual environment.
- Internet Explorer & Service Packs: Microsoft does not support sequencing of any version of Internet Explorer.
- Roaming Profiles: The default local cache location is %APPDATA%, this resides inside a folder that travels with roaming profiles, and will cause applications to fail often as files fail to sync using current best practices for roaming profiles in Windows Vista and Windows 7. Users will have to exclude the Softgrid Client folder from their syncing rules, or use an alternative location.
