Provisioning, maintaining and using traditional computer desktops present many challenges. User satisfaction is low, maintenance costs are high, and stories of lost data, hacked networks, and virus, worm, and DOS attacks are reported almost daily in the press.
As Credit Suisse noted recently in a report on desktop virtualisation: "What began as a useful tool that boosted productivity has grown into a bloated device requiring constant upgrades and maintenance due to compatibility issues associated with patches, new hardware, and software releases."
Many IT departments are considering using virtual desktop infrastructure (VDI) to centralise and virtualise user desktops in a secure location, leveraging data centres and putting the desktop close to support staff.
However, what about performance, cost, and customisation? Many deployments of centralised desktops have effectively delivered the centralisation part, but for the most part have been a shared resource, affording very little in customisation and little general applicability to multimedia or graphics-rich applications.
Cost considerations
The virtual machine approach delivers a fully malleable computer environment, since it is essentially a complete desktop computer stored on a server in a data centre.
Yet, only within the past year or two have client communications protocols developed the level of performance to deliver virtual machine-based desktops satisfactorily.
These protocols eliminate any user perception of latency and slow screen refresh to deliver traditional computer-like graphics performance over all but the slowest of corporate wide area networks (WANs).
What about cost and complexity? One might expect that replacing a lot of computers with centralised CPUs and multi-terabytes of disc storage to keep the personalised operating systems (OS) and applications is going to be extremely expensive.
Given the current availability of fast, multi-core, multiprocessor 64-bit servers, dozens of desktop sessions can be very efficiently hosted on a single machine.
However, the storage scenario is the harder nut to crack. Keeping full OS images in the data centre to load into each virtual machine is hugely wasteful and very difficult to manage. The use of image cloning (starting from a single OS image and delivering copies to the virtual machines) can save storage space, but as soon as the original OS image needs to get patched, all persistence is lost and the clones must be regenerated and distributed. A modern approach to virtualisation offers two best practices to address these concerns.
Performance issues
A new way of delivering desktops to users demands new ways of managing these desktops for an organisation.
Nick Keene is country manager of Citrix Systems Southern Africa.
The first best practice focuses on a separation of the OS from the applications via application virtualisation. This kind of technology can deliver a lot more applications directly to a virtual desktop.
This means a best-performing application can be delivered to a best-performing unencumbered desktop OS, without storing the application on the virtual machine. These can be presented to the user's virtual machine via the client communications protocol or streamed to the desktop virtual RAM via client-side virtualisation, allowing the user access to an application offline.
In either case, only one copy of the application needs to be stored and maintained. This copy can be streamed or presented to thousands of users on demand, without impacting licensing terms for most applications.
The second best practice is to maintain a single, clean, updated OS image for all desktop clients. OS streaming or virtual OS provisioning eliminates storage and support issues by doing away with the need to keep one OS image for each virtual desktop. Instead, one optimised, corporate-standard Windows XP or Vista image is maintained on the network.
All the virtual machines Pre-Execution Environment boot this same image over the network and user-specific configuration/profiles are applied at logon. Because all images are delivered by reference via streaming, users always run the latest patched OS version. You no longer need to patch or change virus definitions for 100, 1 000, or 10 000 desktops. It can now be done once on the golden OS image and is delivered to each user the next time they log on.
A new way of delivering desktops to users demands new ways of managing these desktops for an organisation. Simply migrating desktops to a centralised location adds just about as many problems as it solves.
Adopting an application delivery infrastructure and provisioning a single OS image are two best practices that can go a long way towards making VDI a reality.
* Nick Keene is country manager of Citrix Systems Southern Africa.
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