Hello all,
Everybody who works with Azure knows that making sure the costs don’t go through the roof is vital. For Azure virtual machines we have a couple of standard cost. These are the running cost for the virtual machines, the network interfaces and the disks. When you have a large AVD environment these disks costs can already be big.
Lets use an example: 200 session hosts running a premium disk can result in 4000 euro disk cost. We can do some automation with our friends from Nerdio to swap the disk to standard HDD when not running but still it’s a big cost.
What would you say if we can eliminate the disk cost entirely? This can be done with the use of Ephemeral disks. Lets have a look at those kind of disks.
When creating AVD session in the past, the CPU and memory of the virtual machines resides in 1 rack in a datacenter. The OS disk is a managed disk on storage in a different rack. The OS disk is attached over the datacenter network onto the virtual machine. This causes a little bit of latency on the virtual machine.
An Ephemeral disk is a disk that is located in the server itself as local storage. Using this type of storage means that it is a lot faster providing more iops. The virtual machines can’t be deallocated because when doing so, the disk is also gone.
This feature is now in public preview to use in the Azure portal. You find all the documentation here.
Important to know is that not every vm size in Azure supports Ephemeral disks. there is an easy way to search for is to use a script from Microsoft that you can find on this page. It requires to open Azure Cloudshell and to give a region and the disk size that you need. In this case for AVD I take 127GB.
You will get an output with the vm sizes that aren’t supported and that are supported but only the type of disk that is supported.
Now that we have checked the vm size that we can use, let’s start creating a new host pool. Very important to know is that you need to use the still in PREVIEW feature Create Session Host Configuration to select Ephemeral disks.
Important is that depending the VM size you select, you get a different option for the disk placement.
After the deployment of the host pool and session hosts, we can see the details off the OS disk in the session host overview.
Lets check the resources that are created and we don’t see a disk in the resource group.
To conclude, if you want to gain more hops for session hosts and save money and disk costs, ephemeral disks are the way to go.
I hope you liked this blogpost and feel free to contact me if you want to discuss this or have any questions.
Until next time