With autoscaling we refer to the system's ability to automatically adjust session host servers' resources (RAM & CPU) according to number of users created in the environment. Autoscale can also automatically create new session host servers when you reach your maximum number of users per server and apply a custom image to configure the new server. 

Note: The resources (RAM, CPU) can also be adjusted manually through itopia Instances module if you disable the autoscale. Make sure you disable the autoscale before manually changing RAM and CPU. Otherwise, the system will scale the resources back to your default amounts.
 
Autoscaling settings can be fully customized according to your preferences. It will automatically add or remove resources and /or instances from the deployment group based on increases or decreases in number of created users.

The following information explains how the default formula works to assign your resources:

Default instances:

PDC server (Primary domain controller): 1 CPU, 5.5 GB RAM, 50 GB storage

FBU/USS instances

0-7 users: 2 CPU, 7.5 GB RAM 

8 -15 users 4 CPU, 15 GB RAM

16 – 25 users: 4 CPU, 26 GB RAM

26 users and more: new USS instance (session host) will be created with 4 CPU and 13 GB RAM on both instances

Optional instances:

BDC/SDC (Backup/Secondary domain controller): 1 CPU, 5.5 GB RAM
RDG1 server (RDS Gateway): 1 CPU, 3.8 GB RAM
RDG2 server (Redundant Gateway): 1 CPU, 3.8 GB RAM
BRK server (Dedicated Broker): 1 CPU, 3.8 GB RAM
FSB (Dedicated file server/Broker): 1 CPU, 3.8 GB RAM

Configure Autoscaling 

If you have Professional plan with itopia, you can configure autoscaling from Cloud Desktops section > Autoscaling. The configuration becomes available once the deployment is launched to cloud. 

Go to Cloud Desktops section and select Autoscaling

If it's the first time you open Autoscaling tab, you will see the default setup. You can change the autoscaling settings to meet your needs related to resource management.

If you have multi-region deployment, first select the region you will be changing the settings for. Otherwise, continue to the next step.
 

If you decide to customize the autoscaling settings, start defining the maximum number of users per server.

When the amount of active (on-cloud) users exceeds your number, new user session server will be created.

Then continue by specifying your requirements on the right You can delete the default configuration to set up your own.

Server specifics: Here you can determine the resources for the instance depending on the number of users.
First choose the min and max number of users per resource setup (always start with 0 for the first entry), then select a Machine type. To add the setting, click on the green + sign. 

The setting will be displayed in the list on the right. Continue the same way till the max number of users per server is reached like in the below example:

Continue below to set up an Image for your autoscaling settings.

Using Custom Images to Configure Autoscaling

You can create your custom images with installed applications and use them to configure your session host servers automatically. You will save time that you'd normally spend installing all the new applications in the newly created session host servers.

You have 2 options when using images for autoscaling:

  1. Use your custom image to create new session host instances. You can keep your current session host configuration and all the new session hosts that will be created by autoscale will be set up using your custom image.
  2. You can use your image to re-configure all your existing session host servers

First, create a custom image following this guide.

Once you created your custom image, go to Cloud Desktops > Autoscaling.

Go to Image drop down and select the custom image you created. It will be listed under "Custom"
You can also select any of the standard images Google offers (Windows 2012 or 2016)

Then decide if you'd like to apply the image to all your session host servers or just the new session hosts.
If you'd only like the image to apply to the session host servers created from now on, leave the option below unchecked:

If you checked the option "Apply to existing USS", the system will delete your existing session host servers and create them again using your image.

Important: Please note that if you selected the image to reconfigure all your existing session host servers the system will leave untouched the session host servers that are combined with file server role ( FBU server). That means that if the image has a different OS version than the initial session host set up, there can be difference in the end user experience.

Once you confirm your configuration, select the time when the changes should be applied. If you select Force update option, the changes will be applied immediately and your servers will reboot.

Click Save.

Note1: After using an image to create new session host servers, make sure to reconfigure the app restrictions in itopia CAS so the settings are applied to the new servers.

Note2: The image that you selected for the autoscale will also be used to create any new 1:1 servers when the option is enabled it for a user. Learn more here.

What happens when autoscaling is triggered?

As previously mentioned, the system scales your resources based on user count. The autoscale is triggered as you add or remove users in Users module or whenever you change the autoscaling settings in the portal. 

Whenever the instance resources need to be updated, you get an alert in the portal that the instances will need to reboot to update. The system asks you to select when you want the resources to be reconfigured (servers rebooted). You can force the change with "Force update" option or schedule it to a specific day and time. 

In case the resource change includes new session host creation, the system will spin up a new instance and create a task for every application that must be installed on the newly created VM. At this moment end user logins are disabled to the new instance.

Note: The new session host will be created in the same datacenter region but different zone (e.g. if you deployed in US- East1-b, the new session host can be created in US-East1-c). The reason is to balance the session hosts.

You need to install all the applications on the instance and mark all the installation tasks as complete in itopia for the end user logins to be allowed in the instance. In other words, once you complete all the installation tasks, system allows logins to the server and scales the other instances resources according to your selected schedule (reboot needed). If you selected "Force update" option, the changes will be done right away.
If you chose a custom image for autoscale, you still get the tasks to install applications but you don't have to install those that are already on the image. The tasks in this case are just a way of confirming the apps were installed.

If there's any obstacle like low IP quota that causes a delay in updating the resources (server creation and re-configuring of the RAM and CPU in existing servers) your schedule to make the updates may change. If because of any delay the schedule you selected is no longer valid, the resources will update at 12 AM local time (according to the time zone selected for that particular deployment).

Disable Autoscaling

You can disable the autoscaling anytime with the button on the top left. 

IMPORTANT: When autoscale is disabled you have to manage the resources (RAM, CPU) manually from Instances module. and you cannot automatically add session host servers as your user count increases.

Autoscaling failed creating a new instance

There can be cases when the autoscaling process is not triggered as it should after adding more users. The conditions for creating new instance were met but you notice that a new instance wasn't created and/ or you get an error message in the portal.
We also notify you when the autoscaling process fails under the bell icon in the top right:

The most common cause is a low Google IP quota. In such case you will get a task in Tasks module to increase the quota so the autoscale can be launched. Once you request the quota increase in Google, you must wait for an email confirmation that the quota was increased.

Once you received a confirmation, you can complete the task to increase quotas and the autoscale will be launched again at the time you scheduled initially.

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