5 6 7 Rs of Cloud Migration

I mentioned the 5 Rs in The Application Portfolio Manager a couple of years ago, and I’m returning to them as they’ve been coming up fairly frequently, and also they’ve become the source of some confusion.

5 Rs

The original[1] 5 from Gartner’s Five ways to migrate applications to the cloud (penned by my awesome friend and former colleague Richard Watson):
  1. Rehost
  2. Refactor
  3. Revise
  4. Rebuild
  5. Replace

6 Rs

Then AWS decided it was 6 Strategies for Migrating Applications to the Cloud:

  1. Rehosting
  2. Replatforming (~= revise but may also have pieces of rebuild)
  3. Repurchasing (~= replace)
  4. Refactoring/rearchitecting (kind of brings refactor and rebuild together)
  5. Retire
  6. Retain (do nothing option, should be periodically ‘revisit’)

7 Rs

And now they’re added #7:
      7. Relocate (for moving VMware VMs from on-prem to VMC)

Don’t mix cross-ply and radial on the same axle

Things start skidding out of control[2] when people start mixing the Gartner 5 Rs with AWS’s 6/7 Rs. There’s some parity, but also significant differences that make it possible to come up with a list of Rs that’s got lots of overlap:

  1. Rehost
  2. Refactor
  3. Revise
  4. Replatform
  5. Rearchitect

Or that’s missing some key treatments

  1. Replace
  2. Rebuild
  3. Repurchasing
  4. Retire
  5. Retain

The second set there is more contrived than the first. But this is a classic case of where a consistent taxonomy is helpful. For that reason I’ve been encouraging people to standardise on the AWS definitions.

Update 4 Aug 2020

Richard Watson commented on LinkedIn that the original framework he presented with Chris Haddad only had 4 Rs:

I guess Recode got split into Refactor and Revise.

Update 8 Sep 2020

Somebody sent me an HP deck from 2011 with their Rs (or Re-s):

  1. Re-learn
  2. Re-factor
  3. Re-host
  4. Re-architect
  5. Re-interface
  6. Replace
  7. Retire

So I guess that’s yet another source of confusion for my former HP(E) colleagues.

Re-learn was our process of helping clients understand what applications they actually had, the infra they ran on, the resources they consumed, the technologies, the quality, etc. We would use that result in Apps rationalization to figure out the best future for each app. We used tooling to help with that as well.

Re-interface was all about interconnectivity between systems. It was enabling applications to share data to open up and consolidate business processes.

The HP Rs trace their root back to Electronic Data Systems (EDS) when cloud was nascent, and weren’t at all focused on cloud migration, but rather the broader topic of application portfolio management (including migration off mainframes).

Update 30 Sep 2020

Watching VMworld 2020 I see that VMware has the following:

  1. Retain
  2. Rehost/Migrate
  3. Replatform
  4. Build and Refactor
  5. Retire

So that’s pretty much 5 of the 6 AWS ones, but notably not including Relocate, which is there specifically for VMware stuff :/

Retire also looks like it’s being used to do the same work as repurchase ‘retire traditional app and convert to new SaaS apps’.


[1] Maybe not so original. Although Gartner folk can trace their Rs back to about 2010 there are people from EDS who recall them from 2005/6 (when cloud was just becoming a thing).
[2] As if Charley Says wasn’t terrifying enough growing up in the 70s, another reason to avoid stranger’s cars was in case they might spin out of control because of the wrong tyre mix.

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