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When should persistent VDI be used over non-persistent VDI?

VDI expert Brian Madden explains why most of today's storage options can handle persistent desktops, and how non-persistence can contribute to VDI failure.

One of the biggest decisions IT professionals need to make when building a virtual desktop infrastructure is whether...

the desktops will be persistent or non-persistent.

With persistent VDI, each desktop runs from a separate disk image and users' settings are saved at each logout and reappear at the next login. Non-persistent desktops do not save users' settings or data when they log out. All the desktops use a single shared disk image -- when a user logs on, what he or she sees is a clone of the master image, and the desktop reverts to its original state every time a user logs out. Persistent desktops can be customized more but also require more storage than non-persistent desktops.

In this answer, VDI expert Brian Madden addresses those differences between persistent and non-persistent desktops. Which is better and why?

Persistent versus non-persistent is a huge, huge issue for VDI.

This is the No. 1 most debated, contested issue in the world of VDI. And like everything, there's no one right answer. It depends on your use case, your history, your skill set, your users and what your needs are -- all those kinds of things.

Now, there are a lot of people who believe (myself included) that non-persistent is the long-term direction of Windows. Non-persistent means your disk image does not persist between reboots -- I log in and all desktops have the same generic image and I can do my job. But as soon as I log off, the image gets thrown away. When I log on again, I get a brand-new image -- it looks like my desktop but it's actually a new image.

So, non-persistent has security benefits. It has management benefits. Absolutely this is the future. That said, this is not the way that Windows desktops work today.

Let's look at a typical company. You have 500 employees and there are 500 laptops. You install something on your laptop and you close the lid. The next morning it's still there. Your laptop is not refreshed from scratch every single morning when you turn it on.

It's the same with your desktops. Your files, the garbage, everything you put in your computer, it persists. It's persistent. So, while many of us agree that non-persistent is the wave of the future and the direction that Windows is going, the reality with today's corporate desktops -- of which there are hundreds of millions -- is that over 90% of them are fully persistent.

For successful projects, don't take on too much

Going from an environment that's fully persistent, where every desktop image is unique, to an environment where everyone is sharing the same kind of mass images, that is a big, big deal. It's very difficult to do that.

Interestingly, a lot of people actually fail at VDI because they try to go from this persistent state -- everyone has full access -- to non-persistent, which is locked down. They try to do that at the same time they try to go to VDI.

Of course, they blame VDI. Hey, VDI was fine. The project failed because you went from persistent to non-persistent and you failed with that.

Today's storage technologies can fully support persistent users in VDI where every single user has his or her own disk images. Today's storage technologies can do this for under $100 per user including hardware and software for everything you put in storage.

If you want to do non-persistent, go ahead and do that later -- but make it a separate project. Or some people can do the same thing in reverse. If you are using persistent desktops today -- which most of us are -- it is a really, really big deal to go to non-persistent. Do not do that at the same time as you're trying to also go to VDI, because now you're taking on two massive projects at once -- these really are two projects that are going to get entangled together, be jumbled and they'll both fail.

So, pick one -- either VDI or non-persistent desktops -- and do that first. It could be either one you want. Then once you're there and stable, you can go ahead and do the other one, and then maybe we'll all end up in a VDI and non-persistent world -- but that's in two separate steps rather than doing it all at once.

Next Steps

How do persistent and non-persistent VDI differ?

Know your project size for successful VDI implementation

This was last published in November 2014

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Brian – good read. Always enjoy your point of view on VDI. The article got us thinking when it stated that persistent vs. non-persistent “is the No. 1 most debated, contested issue in the world of VDI." Maybe it was a few years ago, but not so much anymore. Both types of desktops are needed - often within the same organization. The decision of whether to implement persistent or non-persistent is now being based on use case, not on the limitations of legacy desktop provisioning technology. The maturation of desktop layering has (finally) ended the debate. We posted a blog to address this topic with a number of real-world VDI customer examples as proof points. Please check it out, welcome your comments. http://blog.unidesk.com/persistent-non-persistent-vdi-layering-ends-debate -Tom Rose, Chief Marketing Officer, Unidesk
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