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.
So what are the differences between AppStacks and Writable Volumes?
AppStacks
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.
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.
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.
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
