Azure Classic vs. ARM VMs: It’s Time to Migrate

We get requests from customers occasionally about whether ParkMyCloud can manage Microsoft Azure Classic vs. ARM VMs. Short answer: no. Since Azure has already announced the deprecation of Azure classic resources — albeit not until March 2023 — you’ll find similar answers from other third-party services. Microsoft advises only to use resource manager VMs. And in fact, unless you already had classic VMs as of February 2020, you are not able to create new classic VMs.

As of February, though, 10% of IaaS VMs still used the classic deployment model — so there are a lot of users with workloads that need to be migrated in order to use third-party tools, new services, and avoid 2023 deprecation.

Azure Classic vs. ARM VM Comparison

Azure Classic and Azure Resource Manager (ARM) are two different deployment models for Azure VMs. In the classic model, resources exist independently, without groups for applications. In the classic deployment model, resource states, policies, and tags are all managed individually. If you need to delete resources, you do so individually. This quickly becomes a management challenge, with individual VMs liable to be left running, or untagged, or with the wrong access permissions.

Azure Resource Manager, on the other hand, provides a deployment model that allows you to manage resources in groups, which are typically divided by application with sub-groups for production and non-production, although you can use whatever groupings make sense for your workloads. Groups can consist of VMs, storage, virtual networks, web apps, databases, and/or database servers. This allows you to maintain consistent role-based access controls, tagging, cost management policies, and to create dependencies between resources so they’re deployed in the correct order. Read more: how to use Azure Resource Groups for better VM management.

How to Migrate to Azure Resource Manager VMs

For existing classic VMs that you wish to migrate to ARM, Azure recommends planning and a lab test in advance. There are four ways to migrate various resources:

• Migration of VMs, not in a virtual network — they will need to be on a virtual network on ARM, so you can choose a new or existing virtual network. These VMs will need to be restarted as part of the migration.
• Migration of VMs in a virtual network — these VMs do not need to be restarted and applications will not incur downtime, as only the metadata is migrating — the underlying VMs run on the same hardware, in the same network, and with the same storage.
• Migration of storage accounts — you can deploy Resource Manager VMs in a classic storage account, so that compute and network resources can be migrated independently of storage. Then, migrate over storage accounts.
• Migration of unattached resources — the following may be migrated independently: storage accounts with no associated disks or VMs, and network security groups, route tables, and reserved IPs that are not attached to VMs or networks.

There are a few methods you can choose to migrate:

• Use the Azure classic CLI — note that you must use classic to migrate classic resources.
• Use PowerShell
• Use open source migration tools, such as AsmMetadataParser or migAz

We recommend that you move toward ARM resources and eliminate or migrate classic resources as soon as you can. Farewell, classic!

Originally published at www.parkmycloud.com on July 21, 2020