Microsoft has recently announced an important new feature for Azure customers running virtual machines. Specifically, the company has introduced automatic OS image upgrades. Currently available in preview, the ability allows Azure scale sets to upgrade across all VMs automatically.
This is important because it helps customers save by reducing costs. In its announcement, Microsoft says “We are continually looking for ways to lower the overall cost of managing cloud infrastructure.”
Maintaining virtual machines by keeping them on the latest OS version can be costly. Developers usually need to patch VM images across individual VMs at intervals (monthly, for example). This is both time consuming and not cost-effective.
The new automation ability for scale sets simplifies upgrading OS images and reduces cost. Once the preview feature is set up, Azure customers will automatically receive new OS images across the scale set when they are published.
Microsoft says that even this automatic process could cause issues. For example, if the process was to occur across all VMs simultaneously, it would cause excessive application downtime. To overcome this, the upgrades will take place across batches of machines. The company says no more than 20% of the scale set will upgrade at once.
Additionally, Microsoft advises customers to configure an Azure Resource Manager policy. Also, the company says an Azure Load Balancer is also recommended. This gives confirmation when each upgraded batch is completed.
In its blog post, the company explains how the automatic upgrades work:
“An upgrade works by replacing the OS disk of a VM with a new one created using the latest image version. Any configured extensions and custom data scripts are run, while persisted data disks are retained. You can opt out of automatic upgrades at any time, or manually initiate an upgrade.
Note: There are no restrictions on virtual machine or scale set size, and auto-OS upgrade works for both Windows and Linux VMs.”
The new ability is currently available in preview. Microsoft says it is compatible with Windows Server 2016 Datacenter, Windows Server 2012 Datacenter R2, and Ubuntu Server 16.04-LTS. More operating system families will be added in the future.