When you start a desktop virtualization project, one decision seems to trump all others: whether you want offline VDI or virtual desktops connected to the corporate network.
For others, the decision regarding offline VDI is a little more complex. You need to consider how much control IT needs over portable systems and whether you need to support a bring-your-own-device (BYOD) strategy.
Nevertheless, there are cases when disconnected virtual desktops make sense. With offline VDI, the virtual hard drive (VHD) and the associated virtualization software or hypervisor are stored and executed on a physical, often portable device such as a notebook PC.
That allows users to run a virtual desktop without connectivity to a data center or remote host. Users can execute local applications such as word processors or office suites, giving them the same abilities as a traditional desktop. But then, the question is: Why not just run a local OS and locally installed applications instead of dealing with the hassle of VDI?
Basically, choosing to support offline VDI comes down to two factors: portability and management. It is much easier to move a VHD from one machine to another than it is to move a physical OS and locally installed applications. What's more, a VHD can be replicated against a master VHD in the data center, allowing the virtual machine (VM) to be backed up whenever it has a connection to the data center.
That replication capability also allows users to relocate their VMs to other hardware, such as a desktop PC in the office or at home, or a temporarily assigned mobile device. There are also significant management benefits from offline VDI for IT departments. By managing the master VHD in the data center, IT can push applications, updates and other changes to the device seamlessly. IT can also enforce security policies, control access and have granular control over settings and other elements on the virtual desktop -- all based on how VHDs are synchronized with master copies in the data center.
More on offline VDI
Ten advantages of disconnected VDI
Using the virtual desktop offline feature of VMware View 4
Using offline VDI vs. local VDI
Other advantages of offline VDI include reduced data center overhead because the hypervisor is running on a local PC instead of a server. Storage needs are sometimes reduced as well, because deduplication technology can reduce the VHD footprint.
Nevertheless, there are some disadvantages to not having virtual desktop connectivity. First, depending on the applications you're running and the hypervisor's needs, the remote system may need significant processing power and storage to effectively run the VM. In many cases, that means low-end desktops, notebooks and laptops may not be able to run an offline VDI session.
Other downsides include a lack of continual control and more complicated support requirements. When a VM is running disconnected, IT has no insight into what's being done on the system and has no direct control over that VM. What's more, traditional support technologies such as remote-control or remote-access solutions are not available to assist with help desk concerns.
Benefits of offline VDI
Perhaps the most significant factors behind selecting offline VDI over traditional, connected VDI comes down to the end-user experience and deployment challenges. To determine which approach would work better for your environment, let's look at what connected VDI has to offer and its requirements.
Connected VDI uses the age-old ideology of running everything on a central system, with endpoints acting as nothing more than dumb terminals. All CPU activity, display processing and other PC-related activities take place on a VM located on a host in the data center.
The big advantage of connected VDI is manageability, which is enhanced by the consistency restraints placed on VMs. In other words, all users can expect a similar computing experience. This works well for the masses, but it fails to satisfy those with unique needs, such as the ability to run specialized applications, control desktop settings and so on.
Other advantages of connected VDI range from better resource control, enhanced security, easier license management, better user support and improved patch management -- but there are downsides, too.
For example, a connected VDI strategy requires a persistent connection between the host and the endpoint. So, it does not lend itself to portability. Plus, overall performance is dictated by the resources available in the data center. Server performance, the number of VMs and other aspects all affect VM performance, and ultimately, the virtual desktop user experience.
If you need to support mobile or remote users, or a BYOD initiative, offline VDI is certainly a possibility. However, if traditional portable technology and locally installed applications are good enough for mobile workers, it's probably not a necessity.
This was first published in July 2012