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Prepare your VMs for cloud portability

The ability to move workloads to the cloud offers many advantages, but make sure your VMs can make a smooth transition.

One of the big trends in IT today is the use of public clouds as extensions of an on-premises data center, but this process can present challenges if your VMs aren't optimized for cloud portability.

Public clouds can provide a level of scalability that may be difficult or impossible to achieve locally, and are therefore a popular choice for running high demand workloads. Of course, configuring an existing virtualization infrastructure to take advantage of public cloud resources presents a number of challenges, such as identity federation and Internet bandwidth management. One of the most pressing challenges however, is that of moving VMs from a local hypervisor to a public cloud.

The exact steps involved in the migration process vary heavily depending on the hypervisors and cloud service providers used. VMware-to-cloud migrations work differently than Hyper-V-to-cloud migrations. Similarly, Amazon has different requirements for importing VMs into EC2 than the requirements Microsoft has established for Azure migrations.

Regardless of which cloud service provider or hypervisor your organization is using, planning ahead can make the migration process a lot easier. There are things you can do today that may improve cloud portability and make it easier to move your VMs to the cloud.

Planning for compatibility

One of the things you can do to improve the cloud readiness of your VMs is to avoid using pass-through disks. Pass-through disks are a feature that allows a VM to make use of a physical disk rather than relying exclusively on virtual disks. When you migrate a VM to the cloud, part of the migration process involves uploading virtual hard disks. That being the case, you won’t be able to migrate a VM if it is using pass-through disks. Therefore, if you think that there is a chance that you may eventually need to migrate some of your VMs to the cloud, then it is a good idea to avoid using pass-through disks. If some of your existing VMs are currently using pass-through disks, it is a good idea to begin making the transition to virtual hard disks unless you have a compelling reason to continue using pass-through disks.

This brings up another important point. Just because a cloud service provider supports migrating VMs from your hypervisor of choice to the cloud, it doesn’t mean all VM configurations are supported. It is important to check with the cloud service provider to see what VM configurations they will support. For instance, some of the big name cloud service providers support migrating Hyper-V VMs, but only if they are configured to use the older virtual hard disk format (VHD-based virtual hard disks). For whatever reason, VHDX files are not widely supported.

Another best practice is to make sure your VMs are running current operating system versions whenever possible. Some cloud service providers don’t care which operating system is running on your VMs, but some do. Amazon EC2 for example, requires the VM be running an operating system that is supported by Amazon. The reason for this is that the VM will actually acquire a license from Amazon as a part of the migration process. If the operating system wasn't supported, then Amazon would have no way of assigning a license to the VM.

Be flexible

One more thing to keep in mind with regard to cloud portability is that your VMs might not be able to retain their exact hardware configuration throughout the migration process. If you are migrating a VM to Microsoft Azure for example, you will likely have to choose a VM size. A VM size is essentially a predefined VM hardware configuration. The VM size determines the number of virtual cores, the amount of memory and the amount and type of storage the VM will receive. Odds are that an existing VM configuration won’t match up exactly to the available sizes, so you will have to pick a size that is a close approximation. The best practice is therefore to take a performance benchmark on the VM during the early part of the migration planning process. That way you can make sure to give the VM the resources it needs in the cloud.

Every cloud service provider does things a little differently. The key to a successful migration is to understand the nuances that are unique to the cloud provider you are using.

Next Steps

How a cloud migration affects existing infrastructure

Planning and executing a private cloud transition

Common cloud portability integration issues

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