Persistent or non-persistent desktops

In this section, we are going to talk about the different types of desktop assignments and the way a virtual desktop machine is delivered to an end user. This is an important design consideration, as the chosen method could potentially impact on the storage requirements (covered in the next section), the hosting infrastructure, and also which technology or solution is used to provision the desktop to the end users.

One of the questions that always get asked is whether you should deploy a dedicated (persistent) assignment, or a floating desktop (non-persistent) assignment. Desktops can either be individual virtual machines, which are dedicated to a user on a 1:1 basis (as we have in a physical desktop deployment, where each user effectively owns their own desktop), or a user has a new, vanilla desktop that gets provisioned, built, personalized, and then assigned at the time of login. The virtual desktop machine is chosen at random from a pool of available desktops that the end user is entitled to use.

If you remember, back in Chapter 1, Introduction to VDI and VMware Horizon 7, we talked about building the composite desktop. This is the model that is used to build the user's desktop.

The two options are described in more detail as follows:

• Persistent desktop: Users are allocated a desktop that retains all of their documents, applications, and settings between sessions. The desktop is statically assigned the first time that the user connects, and is then used for all subsequent sessions. No other user is permitted access to the desktop.
• Non-persistent desktop: Users might be connected to different desktops from the pool each time that they connect. Environmental applications, or user data does not persist between sessions and is instead delivered as the user logs on to their desktop. The desktop is refreshed or reset when the user logs off.

In most use cases, a non-persistent configuration is the best option; the key reason is that, in this model, you don't need to build all the desktops upfront for each user. You only need to power on a virtual desktop as and when it's required. All users start with the same basic desktop, which then gets personalized before delivery. This helps with concurrency rates. For example, you might have 5,000 people in your organization, but only 2,000 ever log in at the same time; therefore, you only need to have 2,000 virtual desktops available. Otherwise, you would have to build a desktop for each one of the 5,000 users that might ever log in, resulting in more server infrastructure and certainly a lot more storage capacity. We will talk about storage in the next section.

The one thing that used to be a bit of a showstopper for non-persistent desktops was around how to deliver the applications to the virtual desktop machine. Now that application layering solutions such as VMware App Volumes are becoming a more mainstream technology, the applications can be delivered on demand as the desktop is built and the user logs in.

Another thing that we often see some confusion over is the difference between dedicated and floating desktops, and how Linked Clones fit in. Just to make it clear, Linked Clones, Full clones, and Instant Clones are not what we are talking about when we refer to dedicated and floating desktops. Cloning operations refers to how a desktop is built and provisioned, whereas the terms persistent and non-persistent refer to how a desktop is assigned to an end user.

Dedicated and floating desktops are purely about user assignment and whether a user has a dedicated desktop or one allocated from a pool on demand. Linked Clones and Full Clones are features of Horizon View, which uses View Composer to create the desktop image for each user from a master or parent image. This means that, regardless of having a floating or dedicated desktop assignment, the virtual desktop machine could still be a linked or full clone.

So, here's a summary of the benefits:

• It is operationally efficient. All users start from a single or smaller number of desktop images. Organizations reduce the amount of image and patch management.
• It is efficient storage-wise. The amount of storage required to host the non-persistent desktop images will be smaller than keeping separate instances of unique user desktop images.

In the next sections, we are going to cover an in-depth overview of the cloning technologies available in Horizon 7, starting with Horizon View Composer and Linked Clones, and the advantages the technology delivers.