Virtual desktop infrastructure (VDI) has faced plenty of challenges: complexity, high cost, heavy server and storage requirements, and end-user dissatisfaction, to list the common complaints. But VDI has also delivered plenty of innovation and experimentation, with vendors taking a variety of approaches to lower the hurdles to implementation, ease the management burden, and address a fuller range of user needs.
One subset of VDI, dubbed client-hosted or offline mode, is an interesting hybrid that takes advantage of local hardware resources -- the PCs and laptops already in users' hands -- while still fulfilling the promise of easier, central management. Naturally, the server and storage requirements for managing desktop images pale considerably to those for hosting all of the desktop computing power in the data center. With offline VDI, there's no need for high-end multiprocessor servers with loads of RAM, and concerns about WAN usage and network latency disappear. Instead of "wasting" local resources on a PC or laptop when remoting into a hosted VDI solution, those resources are put to good use.
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The difference between offline VDI and a traditionally installed desktop, of course, is virtualization. The desktop OS runs on the local hardware in a virtual machine, abstracted from the underlying hardware via a hypervisor. Because the hypervisor runs the show, an endpoint can run multiple instances of different operating systems and keep them completely isolated from one another. IT maintains control over the VM running on the endpoint by way of centrally stored golden images and endpoint policy enforcement.
Local desktop virtualization, central management
Virtual Computer's NxTop Enterprise is an offline mode VDI solution that provides a structured and secure management platform and a highly efficient client hypervisor based on open source Xen. Virtual machine creation, user administration, and policy enforcement take place in NxTop Center while the virtualization hypervisor, NxTop Engine, runs on local hardware and uses local resources. I found NxTop Enterprise to be a fast and intuitive way of deploying and managing client-side virtual desktops. The browser-based user interface is extremely easy to navigate, and the policies you can apply to VMs provide a great deal of control.
NxTop Center is where all VM creation, maintenance, and assignment take place. While it requires a Windows Server 2008 R2 server with the Hyper-V role enabled, Hyper-V is used only for virtual machine creation and maintenance -- not for hosting NxTop Center (which installs natively, not in a VM) or the execution of endpoint VMs. NxTop Center also ties in to Active Directory so that VM-to-end-user assignment is quick and easy.
Building out a virtual machine is a straightforward process of importing an operating system ISO image into NxTop's software library and running through the virtual machine creation wizard. During this process, admins can provide their volume license information (for Windows machines), define the virtual hardware (processor count, RAM, and disk size), and apply policies such as OS expiration, USB permissions, power management settings, and lockout settings -- that is, how long the virtual machine can go without contacting the management server before the user is locked out.
On completion, NxTop Center spins up the new VM in Hyper-V and saves the image in the virtual machine library. Windows XP through Windows Server 2008 are supported as managed guests, with limited support for Linux. Virtual Computer states that just about any x86 OS can be successfully installed into a VM and deployed by NxTop Center, but official support is limited to Windows.
During my testing, I deployed a Windows XP Pro VM and two different Windows 7 Pro VMs to my test MSI laptop. From the NxTop Launcher application, I could pick and choose which VMs to start, as well as easily click between them. Had I been so inclined, I could have run a Windows Server VM on the same hardware. The only limitation is the amount of local hardware resources.
Like any virtual machine manager, NxTop Center allows IT to maintain multiple versions of its virtual machines. For example, I created a new version of a Windows 7 VM after applying the latest batch of Windows updates. After deploying it to an endpoint, I easily rolled back to an earlier version and soon had the laptop back online -- a great option for swift recovery in case there's a problem with a newly deployed VM. NxTop doesn't send the entire virtual disk to NxTop Engine. It only sends the changes, which are stored in a separate, differencing disk, greatly reducing the amount of data transferred. Updates take place automatically whenever an endpoint connects back to NxTop Center.
All your VM are belong to us
One of the most powerful aspects of NxTop Enterprise is the policy engine. A set of policies for each VM defines everything from when the virtual machine expires to USB and Windows settings. The policy engine goes beyond simple hardware control, allowing IT to define granular lockout policies and whether to preserve Windows event logs, file system shares, and the user download folder. I was able to create a Windows XP VM with a policy that disabled all USB access and allowed the VM to be used for only 30 days. IT can create its own custom policies or use the built-in policies to quickly deploy VMs. NxTop Center even provides a "green" policy that specifies power settings for the endpoint.
NxTop Engine is a true Type 1, "bare metal" hypervisor that runs on late-model PCs and laptops. Based on the open source Xen hypervisor, NxTop Engine requires a system that has Intel or AMD hardware virtualization support built into the motherboard, along with at least 2GB of RAM for one virtual machine (plus 1GB for each additional VM) and an Intel, Nvidia, or ATI graphics processor. I installed NxTop Engine on an MSI laptop with an Intel i3 CPU and 4GB of RAM.
On first boot, my assigned VMs began the process of downloading from NxTop Center. Even though the VMs are compressed, it still takes some time to copy the initial image, so this is best done on a local network connection and not over the Internet. Note too that NxTop Engine requires a "blank" disk partition to install into. Because I didn't want to overwrite the operating system already present on my laptop, I had to use a disk partitioning utility to make room for my installation.
One interesting feature of NxTop Engine is that the launcher application doubles as a pseudo Chromebook. NxTop Connect is a lightweight shell that allows the end-user to launch Google Chrome or Remote Desktop Connection while waiting for a VM to start or update. It's not really a tool for everyday use, but it's a nice touch for those of us who just can't wait to get online.
Offline mode VDI combines the rich benefits of virtualization with centralized deployment and management, while still allowing an endpoint to be an endpoint. NxTop Enterprise hits the target on both sides of this equation. NxTop Center is intuitive to use, and I was impressed by how quickly I could create and update my VMs. On the client side, the VMs running in NxTop Engine worked flawlessly and without any hint that they're virtual. The OS support covers all the Windows bases, and the policy engine handles just about every situation. Of course if you're looking for tablet and smartphone support, you won't find it here. But any IT shop interested in VDI and easing Windows desktop management without giving up fat endpoints should take a look at NxTop Enterprise.