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The benefits of software virtualisation

Quoting IT PRO

Speak to most IT marketing professionals, and they will try and convince you that virtualisation is a new phenomenon. In truth, the concept of running one program inside another has been around for years.

Ten years ago, Sun popularised the notion of virtualisation with Java. The system's innate portability was due to a virtual machine that created a sandbox for secure applets. IBM has also used a hardware abstraction layer to separate applications from the underlying systems in its enterprise machines.

Today, the concept of virtualisation has evolved. Companies like VMWare and Xen have promoted the notion of running a whole operating system, either on top of another, or atop a hardware-based Hypervisor. However, some companies are now preaching application virtualisation, in which software applications are insulated from the underlying operating system using an insulating layer. The layer protects the application from the registry, causing system alterations to be written to an alternative store, so that the underlying operating system remains unchanged.

Differentiating virtualisation

One of the differences between some of today's application virtualisation systems and the Java virtual machine is that the applications are conventional pre-compiled applications, ostensibly installed on the computer just like any other application and run natively. The JVM, on the other hand, interpreted the code or ran it using a just-in-time compiler, contained in a resident virtual machine.

Why would an IT department want to deploy applications in this way? Lower support and maintenance costs are the obvious answer. "People mostly use imaging tools or [Microsoft's] Systems Management Server to deploy operating system images that include applications," says Scott Reynolds, a consultant at IT consultancy Morse, describing the traditional way of rolling out corporate software. "If that's your mechanism, then every time you have to update an application, it creates additional workload and increases the load on the network."

"An organisation will go through a testing phase where they test all of their applications alongside each other, for conflicts. The largest organisations have more applications, and multiple versions thereof. If you can choose your testing timeframe or even eliminate it entirely, then that is something that application virtualisation will bring you."

It becomes possible with some systems for IT departments to install and uninstall applications more easily, often with a single click, or even for an employee to run an application or server from a USB key on a different machine.

Creating a self-contained software environment

Ideally, virtualised applications will be able to run atop their own insulated software layers without causing conflicts within the operating system. In some instances, different versions of the same application can be run alongside each other (handy if you want to beta test Office 2007 without abandoning Office 2003, for example, or ease the transition from one application to another).

Even Microsoft is now using elements of application virtualisation within the Vista operating system. Under its User Account Control regime, users are encouraged to run programs under standard accounts, to restrict privileges. Many software applications are designed to run in privileged mode, especially for activities like changing the registry. The system uses a virtual registry to enable applications to run in a less privileged mode.

Different vendors will define application virtualisation differently, according to their products' characteristics. Ardence, for example, argues that virtualisation can include application streaming. Its Software Streaming Platform product is designed to reset the BIOS of a system to boot an operating system from the network drive, essentially running any operating system on the 'bare metal', caching nothing locally on the PC but downloading operating system and application code for local execution. It differs from products like Citrix's Metaframe in this regard because it is locally executing code, rather than simply executing it on a server and streaming a screen image to the client.

Jeff Hibbard, vice president of marketing for Ardence, argues that the company is virtualising both the operating system and the applications running on it. But this system doesn't inherently provide what many experts such as Gartner vice president Brian Gammage consider to be virtualisation's core characteristic: isolation.

Application isolation involves taking an application and wrapping it in a virtual software layer to shield it from the operating system. "The intelligent thing is that it convinces each application that it is the only application," explains Morse's Reynolds.

Technology from another application virtualisation firm, Thinstall, packages an application into a single .exe file that includes a software 'wrapper adding an additional 300Kb of hard drive space (and 1Mb of RAM during execution) to the application's disk footprint. The wrapper replaces the Windows loader, and streams the application's code into the local PC's memory from wherever the .exe file is stored (say, on a network drive or a USB key). The wrapper then acts as a virtual sandbox for the application, using a virtualized file system and registry for data storage and configuration. Thinstall's software runs all applications in standard user account mode, explains CTO, president and founder Jonathan Clark, which means that it couldn't write directly to the Windows registry even if it wanted to.

That brings deployment and management benefits but it also creates challenges. Applications requiring device drivers, for example, are currently difficult if not impossible to virtualise using Thinstall. "We don't support applications that have device drivers right now. They would include things like antivirus products and personal firewalls," says Clark.

Read the rest of the article, here.

Published Monday, October 16, 2006 6:22 AM by David Marshall
Filed under:
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