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VMware virtual desktop infrastructure (VDI) started as a customer-built solution to rapidly deploy Windows desktops and has ballooned into a full product offering. However, VDI is still in its infancy, and we have not yet realized the full potential of virtual desktops. This article will outline some of the limitations of VDI and how they can be eliminated, as well as some possible future VDI deployment scenarios.
VDI: The road to VMware Virtual Desktop Manager 2
VMware VDI spawned from the ideas of some creative VMware customers. Customers that had virtual infrastructures that included VMware ESX server thought, "Why not just install Windows XP as a guest virtual machine on our ESX server?" The clients could then connect to the virtual machine via remote desktop protocol (RDP). This idea later became what's known today as VMware VDI. There is a connection broker piece in the VDI that manages the connections from clients to the hosted Windows XP virtual machines. In the past, this was provided by a third party. However, VMware announced on September 10, 2007 that it would be offering its own connection broker called Virtual Desktop Manager 2. At time of publication, VMware is currently offering Virtual Desktop Manager 2 as a beta.
The way that VMware VDI works is that a client machine (desktop, thin client, etc.,) has a RDP connection via the connection broker to a guest VMware Infrastructure 3 (VI3) virtual machine. There are currently some disadvantages to this approach. First, storage needs to be allocated to each guest virtual machine that will be used by the clients. At 10-to-15 GB per machine, this could add up quickly. Second, virtual machine patch management. A Windows machine is a Windows machine, whether physical or virtual.
Citrix Provisioning Server for Datacenters 4.5
One of the ways to overcome the patch management disadvantage today is to combine the VDI solution with Citrix Provisioning Server for Datacenters 4.5. Citrix Provisioning Server is able to stream a shared disk image (operating system and application stack) to a physical or virtual machine. In this case, the disk image would be streamed to the VMware ESX guest virtual machines. Since the guest virtual machines' virtual hardware should have uniform drivers, there would only need to be multiple disk images if there were multiple application stacks. The company might even be able to get away with a single disk image if the applications were streamed or deployed on demand from another solution. With a single disk image, patching can be handled on the single image. When the guest virtual machines reboot, they will get the newly patched disk image. This dramatically cuts down on the amount of storage required for a VDI solution.
From the server to the desktop with VMware OnDemand streaming technology
In the not too distant future, VMware VDI solutions will move from the server to the desktop. Apart from patch management, one of the other disadvantages with server-based computing is loss of connectivity: users then can't access their virtualized desktops and/or applications. Enter VMware ESX 3i. Suppose the ESX 3i hypervisor was embedded in a desktop. Since ESX 3i supports Serial Advanced Technology Attachment (SATA) disks, there is an opportunity to stream a single VMware image from a server and have it cached and run on the local desktop. VMware is working on a product called VMware OnDemand streaming technology that should be able to accomplish this.
The system would work something like what follows: A desktop-like client with ESX 3i boots, and a VMware guest image is streamed to the client and stored on a local SATA drive for offline use. Instead of the processing taking place on the ESX server in the data center, the desktops become ESX servers themselves and perform the processing locally. The system administrator would still only have one disk image to patch and manage. Also, the clients could still run applications locally if there was a connectivity disruption.
I believe this could be in the future for VDI deployments. VMware ESX 3i supports SATA disks that are already a standard on desktops and laptops, OnDemand streaming technology from VMware should be coming soon, and businesses will continue to need flexibility with a mix of distributed and server-based computing resources. It is an exciting time for virtualization technology and VDI solutions.
About the author: Harley Stagner has a wide range of knowledge in many areas of the IT field, including network design and administration, scripting and troubleshooting. Of particular interest to Harley is virtualization technology. He was the technical editor for Chris Wolf and Erick M. Halter's book, Virtualization: From Desktop to the Enterprise and currently writes his own blog at www.harleystagner.com.