Weighing connected vs. disconnected VDI

Offline VDI lets users work from anywhere -- even without an Internet connection -- but that brings up a few challenges regarding user experience.

When it comes to virtual desktop infrastructure, administrators have a lot of choices. You may have wondered about the differences between VDI software options, remote display protocols or all the licenses out there. In this series, we tackle some of the biggest head-scratchers facing VDI admins to help you get things straight.

Lets Get This StraightYou can set up a virtual desktop infrastructure in one of two ways: connected or disconnected. So which one is right for you and your users?

Connected, or online, VDI means that the virtual desktop is connected to the data center network and all processing happens on the virtual host. Disconnected, or offline, VDI means that the desktop is not connected to the network and the virtualization software and hard drive run directly on the client device. Some VDI software offers both modes, so users can jump offline at any time and move their desktop with them.

Each approach comes with benefits and downsides, and your choice will affect network connectivity, device portability and security. Let's dig into the differences and get this straight.

Benefits of disconnected VDI

There are a few ways to do offline VDI. Some VDI tools synchronize virtual machines (VMs) so users can access them in the office, then access the same VM from a laptop offline somewhere else, for example. Another method, known as checking in, lets users take the VM offline, then check it back into the desktop pool when they get back online -- at which point the data refreshes on the host.

The biggest benefit to disconnected VDI is that users can access their data and applications from any location, even without an Internet connection. That means they could log into their desktop on a mobile device from a hotel room, for instance. Users also like disconnected VDI because it generally allows for greater desktop personalization. IT can set up virtual desktops to store a user's files and preferences -- even letting those desktops move from device to device with the user, whether connected to the network or not.

To make sure the endpoint devices are still secure, administrators can encrypt hard drives and apply security policies that will remain during both online and offline modes. Plus, IT can configure automatic backups so the desktop gets backed up to the data center when the user reconnects to the network. When it comes to disaster recovery, offline VDI actually makes things easier. Users can still get to their data and applications even if a disaster situation brings down the data center.

Series: Let's get this straight

Comparing remote display protocols

Application virtualization smackdown

Clearing up Microsoft VDI licensing: SA vs. VDA vs. CDL

How cloud-hosted desktops differ: Comparing VDI, DaaS

Finally, offline VDI helps bring down hardware and deployment costs. It may lessen the need to upgrade hardware, since offline desktops can run on pretty much any machine. Storage needs may also be reduced using deduplication technology, but that's a tricky area because offline VDI can also hike up the cost of storage over a remote connection.

Disconnected VDI downsides

The big question with disconnected VDI is the following: If you can run the desktop offline on a client device, then why are you doing VDI in the first place? Hosting virtual desktops centrally in the data center can be expensive and complex, so if you're always using offline mode, then there's no reason to allow online mode at all. It’s worth a look at how often users will be accessing offline vs. online VDI.

Plus, offline VDI doesn't always provide the best user experience. Syncing the desktop when accessing it offline can be very slow on poor connections. In fact, it's not always possible to do offline VDI on all devices. It takes a lot of processing power to run the virtual desktop, so some lower-end notebooks or laptops might not be able to support a VDI session.

Finally, it's important to make sure you understand the difference between disconnected VDI and client-based virtualization. Local VDI products that run virtual machines on the client device can provide offline capabilities, but they're not the same thing as offline VDI. Client hypervisors can provide offline access as well, but they're not all that practical for offline virtual desktops today. Client hypervisor technology has struggled to become user friendly and support an ever-growing hardware base.

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