App Volumes installs an additional virtualization layer on top of the guest operating system which detaches the application, user settings, and user data layers from the virtual machine (VM). As a result, applications, user settings, and user data become independent from the VM and can be moved across data centers and shared with other VMs.
In a traditional vSphere deployment, a VM consists of a guest OS, applications, user settings, and user data all in a single VMDK file. A copy of the VMDK file is created on the vSphere datastore for every user of a VM. You cannot manage applications, user settings, and user data independently of the VM.
App Volumes detaches the guest OS from the applications, user settings, and user data by installing the App Volumes agent on top of the guest OS. With App Volumes, you deliver applications and user settings through two types of containers, AppStacks and Writable Volumes. AppStacks and Writable Volumes are VMDK files that reside on top of the App Volumes agent. Unlike the traditional VM architecture, only one copy of each AppStack and Writable Volume exists on the vSphere datastore. You can manage AppStacks and App Volumes independently of the VM.
AppStacks are read-only containers that you can use to deliver applications to your users. You can create multiple AppStacks and provision them with different sets of applications depending on the needs of your users. For example, you can create one AppStack with development tools and another one with core applications such as Microsoft Office.
You assign AppStacks to Active Directory user or computers accounts, groups or OUs . When a user logs in to a VM, the AppStack is attached to that VM and the applications on the AppStack become available to the user.
You can change or update the applications in every AppStack individually and deliver the new version of the AppStack to your users.
For information about how to create and manage AppStacks, see Working with AppStacks.
Writable Volumes are read-write containers that you can use to enable your users to install their own applications and to store their settings. Writable Volumes can migrate with their users across different computers and systems. One user can use only one Writable Volume at a time.
For more information about Writable Volumes, see Working with Writable Volumes.