Gartner Research

Migrating Applications to the Cloud: Rehost, Refactor, Revise, Rebuild, or Replace?


The CIO issues a simple directive: "Move some applications to the cloud." To do this, architects face bewildering choices. In this Decision Point, Principal Research Analyst Richard Watson steers architects to a choice from among five alternatives: Rehost on HIaaS, refactor using SIaaS and PaaS, revise for HIaaS or PaaS, rebuild on PaaS, or replace with SaaS. The decision must consider an organization's requirements, evaluation criteria, and architecture principles. However, no alternative offers a silver bullet: All alternatives require architects to understand application migration from multiple perspectives and criteria, such as IT staff skills, existing investments, and application architecture.

Published: 03 December 2010

ID: G00207162

Analyst(s): Richard Watson

Table Of Contents

Decision Point

Decision Context

  • Business Scenario
  • Architectural Context
  • Related Decisions

Evaluation Criteria

  • Requirements and Constraints
    • Migration Goals and Priorities
    • Legacy Application Characteristics
    • Modernization Requirements
    • Application Platform and Architecture Principles
    • Development and Operations Skills Constraints
    • Migration Cost Considerations
  • Principles


  • Rehost
  • Refactor
  • Revise
  • Rebuild
  • Replace
  • Comparing Alternatives
  • Distinguishing Products from Services

Future Developments

  • Progress on Portability Standards
  • Evolution of Cloud Business Models
  • Incumbent Platform Players Will Wake Up

Decision Tool

  • Pre-Decision Assumptions
    • Assumption 1: Quality of Service Risks
    • Assumption 2: IT Portfolio Management Frameworks
  • Using the Decision Tools
    • Decision Filters
    • Migration Goals Assessment Tool

Decision Justification

  • Use Rehost
  • Use Refactor
  • Use Revise
  • Use Rebuild
  • Use Replace

Recommended Reading

Revision History


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