The six Rs of cloud migration (retire, retain, replace, rehost, re-platform, and refactor), have been a staple for many years. I’m not sure where they came from, but you’ll find them listed in one form or another on many cloud migration project slides.
The reason for the six Rs is simple. We have workloads, which are typically applications and coupled data not running on a cloud, and we’re looking to place them into categories as to what will be done with them in the future, in the cloud or not. Here’s the short explanation of the six Rs:
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Retire: Remove a workload entirely or end of life it.
Retain: Keep it where it is.
Replace: Find SaaS systems or other analogs for the workload.
Rehost: Lift and shift it, or just move it to the cloud with few or no modifications. For example, move from Linux on premises to Linux in the cloud. I see this differently than refactoring, in that we’re just changing an application so it runs well on a cloud platform and not specifically leveraging cloud-native services.
Re-platform: If we can’t find platform analogs on the target cloud, we move to a new platform, such as Linux to Windows. Sometimes new databases and other platforms change as well. Thus, the workload needs to be modified to accommodate the new platform, but we’re not leveraging cloud-native services.
Refactor: Heavily modify (re-code) the workloads to take advantage of cloud-native features such as cloud security, governance, monitoring, auditing, etc.
Of course, just to confuse things, I’ve seen the six Rs with different terms (such as “repurchase” instead of “replace”) or even different definitions of the Rs. So, don’t get on me if what you’re using does not match the above exactly. For our purposes it really does not matter.
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