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App Volumes AppStacks vs. Writable Volumes

By Dale Carter, Senior Solutions Architect, End-User Computing

With the release of VMware App Volumes I wanted to take the time to explain the difference between AppStacks and Writable Volumes, and how the two need to be designed as you start to deploy App Volumes.

The graphic below shows the traditional way to manage your Windows desktop, as well as the way things have changed with App Volumes and the introduction of “Just-in-time” apps.

DCarter AppVolumes v Writable Volumes 1


So what are the differences between AppStacks and Writable Volumes?


An AppStack is a virtual disk that contains one or more applications that can be assigned to a user as a read-only disk. A user can have one or many AppStacks assigned to them depending on how the IT administrator manages the applications.

When designing for AppStacks it should be noted that an AppStack is deployed in a one-to-many configuration. This means that at any one time an AppStack could be connected to one or hundreds of users.

DCarter AppVolumes v Writable Volumes 2


When designing storage for an AppStack it should also be noted that App Volumes do not change the IOPS required for an application, but it does consolidate the IOPS to a single virtual disk. So like any other virtual desktop technology it is critical to know your applications and their requirements; it is recommended to do an application assessment before moving to a large-scale deployment. Lakeside Software and Liquidware Labs both publish software for doing application assessments.

For example, if you know that on average the applications being moved to an AppStack use 10 IOPS, and that the AppStack has 100 users connected to it, you will require 1,000 IOPS average (IOPS pre-user x number of users) to support that AppStack; you can see it is key to designing your storage correctly for AppStacks.

In large-scale deployments it may be recommended to create copies of AppStacks and place them across storage LUNs, and assign a subset of users to each AppStack for best performance.

DCarter AppVolumes v Writable Volumes 3


Writable Volumes

Like AppStacks, a Writable Volume is also a virtual disk, but unlike AppStacks a Writable Volume is configured in a one-to-one configuration, and each user has their own assigned Writeable Volume.

DCarter AppVolumes v Writable Volumes 4


When an IT administrator assigns a Writable Volume to a user, the first thing the IT administrator will need to decide is what type of data the user will be able to store in the Writable Volumes. There are three choices :

  • User Profile Data Only
  • User Installed Applications Only
  • Both Profile Data and User Installed Applications

It should be noted that App Volumes are not a Profile Management tool, but can be used alongside any currently used User-Environment Management tool.

When designing for Writable Volumes, the storage requirement will be different than it is when designing for AppStacks. Where an AppStack will require all Read I/O, a Writable Volume will require both Read and Write I/O. The IOPS for a Writable Volume will also vary per user depending on the individual user and how they use their data; it will also vary depending on the type of data the IT administrator allows the user to store in their Writable Volume.

IT administrators should monitor their users and how they access their Writable Volume; this will help them manage how many Writable Volumes can be configured on a single storage LUN.

Hopefully this blog helps describe the differences between AppStacks and Writable Volumes, and the differences that should be taken into consideration when designing for each.

I would like to thank Stephane Asselin for his input on this blog.

Dale is a Senior Solutions Architect and member of the CTO Ambassadors. Dale focuses in the End User Compute space, where Dale has become a subject matter expert in a number of the VMware products. Dale has more than 20 years experience working in IT having started his career in Northern England before moving the Spain and finally the USA. Dale currently hold a number of certifications including VCP-DV, VCP-DT, VCAP-DTD and VCAP-DTA.

For updates you can follow Dale on twitter @vDelboy

13 thoughts on “App Volumes AppStacks vs. Writable Volumes

  1. Harman

    The above expatiation is indeed helpful… thanks for efforts to write it….

    I have question ….

    Can we use writeable volumes on RDSH environment….

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  3. Shiraz A. Farooqui

    Nice blog Dale! The one-one and one-many examples are good enough to differentiate. However, we face a strange issue when using Appstack and not sure if its the design or a bug.
    Any user who has a full clone machine and is assigned an Appstack, the machine would not save an application changes (install/uninstall) . This is any application installed on C:\. Even if a folder is saved on C:\ and the machine restarted its lost if the user/machine has an Appstack assigned. Initially when discovered it was a big surprise and we failed to understand what was going on … as if a snapshot of the machine was rolling back itself upon restart. When appvolumes agent was stopped and the user was not assigned any Appstack the problem did not re-occur. So now we simply do not assign any Appstack to FULL CLONE machine users.
    Please shed some light.

    1. Alawi Albar

      AFAIK, AppVolume agent virtualize the OS so that any change users make during their session will be lost after logging out. The AppStack is always read-only and so any updates to applications are not allowed. However, with AppVolume’s Writable Volumes your users can persist any change they make during their session by redirecting changes made to the C:\ drive to the hidden VMDK (or VHD) disk (i.e. to the Writable Volume).

      That’s being said, it seems that AppVolume is designed to work best with non-persistence desktop rather than persistence ones!

  4. sandy

    Hi, I have query:
    I have an application which has “Clickonce” shortcut, This will download the files to %Localappdata%\ location.
    Can we create a writable volume for this?

  5. Dan K

    “create copies of AppStacks and place them across storage LUNs, and assign a subset of users to each AppStack for best performance.” How does one do that, without going through the whole process all over again?

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  9. Anthony Morey


    How does one get a writeable volume to “roam” across different Blocks of 2000 user compute resource. Block1/VC1, Block2/VC2 and Block3/VC3.
    Currently in testing it seems to only connect to the first block from which the template was uploaded.


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