App Attach Azure files limits

Eoin Mackintosh 5

I am hitting App Attach limits on AVD with a customer with errors mounting apps on devices. Based on the Microsoft documentation - https://learn.microsoft.com/en-us/azure/storage/files/storage-files-scale-targets#app-attach-with-vhdvhdx, the Azure files location should not be hitting any limits. Has anybody used this to calculate maximum apps per Azure files location and IOPS requirements as when I calculate it out not getting anywhere close to what actually seeing. Have a mixture of Multi-Session non-persistent and Single-Session persistent AVD devices and a dedicated Azure files location just for App-attach. Just trying to set limits for number of apps, user and devices that can be located in a single Azure files location. Checked both IOPS and handles. Any help or thoughts appreciated. Keen to understand what happens on Multi-session devices if have 10 users on single device...does it get counted as single device from an app-attach perspective (as per the link) or one per user session. We assign App Attach packages to a user group, but addition if apps are made available to a user group but also have to assign to a host pools for them to use....so will all the devices in the host pool get the app from a Azure files limit perspective...or only the devices in the host pools for which the user is assigned an app? Any help appreciated.

Mahesh Goud Juvvadi 1,950 Reputation points Microsoft Vendor

2025-02-07T20:34:27.7333333+00:00
Hi Eoin Mackintosh,

Thank you for reaching out to the Microsoft Q&A platform.

Could you please share us the below following details:

How many single-session and multi-session VMs do you have in your AVD environment and number of users per multi-session VM?

Please share me the error screenshot while you are mounting apps on devices for better understanding and assistance.
Mahesh Goud Juvvadi 1,950 Reputation points Microsoft Vendor

2025-02-10T17:54:48.3+00:00

Hello Eoin Mackintosh,

Could you please go through the last comment and provide us the required information to troubleshoot further.

Thank you.
Eoin Mackintosh 5 Reputation points

2025-02-11T16:31:19.0133333+00:00

We have 1600 single session devices (but rapidly removing from App Attach) and we have about 70 multi-session devices with around 12 users on each. The multi-session pool only reaches about 50 devices going online over the course of the day so up to 600 users on MS devices.
Keshavulu Dasari 3,790 Reputation points Microsoft Vendor

2025-02-11T20:19:19.6+00:00
Hi Eoin Mackintosh ,

I understand according to the Azure Files scalability and performance targets, the limits are per VM mounting the image, not per user. This means that for multi-session devices, the limit is counted per device, not per user session.

For IOPS, the performance of Azure Files can be influenced by various factors, including the type of storage account and the tier you are using (Standard or Premium). Premium storage offers higher IOPS and throughput compared to Standard ,

On multi-session devices, the app-attach limit is counted per device, not per user session. So, if you have 10 users on a single device, it is considered as one device from an app-attach perspective.

Additional information,

App Assignment to User Groups and Host Pools:

When you assign App Attach packages to a user group, the apps are made available to all users in that group, for the apps to be usable, they also need to be assigned to the host pools.

From an Azure Files limit perspective, only the devices in the host pools where the user is assigned an app will count towards the limit.

Handling Large Numbers of Devices and Users:

With 1600 single-session devices and 70 multi-session devices, it's crucial to monitor the open handles and IOPS. Azure Files has limits on the number of open handles per root directory, directory, and file. Ensure that your setup does not exceed these limits.

For more information
https://learn.microsoft.com/en-us/azure/virtual-desktop/app-attach-overview?pivots=app-attach

If you are still facing issues, please provide some screenshots and details in the "comments" and I would be happy to help you.
Keshavulu Dasari 3,790 Reputation points Microsoft Vendor

2025-02-13T18:49:06.3266667+00:00

Hi Eoin Mackintosh ,

Just checking in to see if the response helped. If you have any questions, let me know in the "comments" and I would be happy to help you.
Eoin Mackintosh 5 Reputation points

2025-02-13T23:14:32.8+00:00

Afraid that doesn’t answer my question. I understand number of IOPS and file handles and how can be calculated per device and user. My problem is that the output of the calculations based on the Microsoft guide bears no resemblance to what we are seeing in the environment. So my question is, has anybody successfully followed the guide and got an answer close to the IOPS etc actually seen in an environment? Either the guide is wrong or we are missing something as consistently hitting limits when the calculation says we should be nowhere close.
Keshavulu Dasari 3,790 Reputation points Microsoft Vendor

2025-02-14T20:07:49.2933333+00:00

Hi Eoin Mackintosh ,

I understand that, here Factors Affecting Performance:

Network Latency: Ensure minimal latency between Azure Files and AVD.

Storage Account Performance: Use Premium file shares and verify no throttling.

Concurrent Access: Monitor simultaneous connections and IOPS ,Use Azure Monitor and Azure Storage metrics to identify bottlenecks and participate in forums for practical tips and shared experiences.

If you have any other questions or are still running into more issues, let me know in the "comments" and I would be happy to help you.
Keshavulu Dasari 3,790 Reputation points Microsoft Vendor

2025-02-17T19:45:34.5666667+00:00

Hi Eoin Mackintosh ,

If you have any other questions or are still running into more issues, let me know in the "comments" and I would be happy to help you.

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App Attach Azure files limits

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