Rehosting
Lift and shift: fastest, cheapest, and capturing none of the benefits.
5 to work through
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intermediate Multiple choice
A data-centre exit must move about 600 virtual machines in nine months. The first wave moved 40 machines chosen because they were the least busy and three business applications became unusably slow overnight. What should decide which machines travel in the same wave?
3 min answer -
intermediate Multiple choice
A data-centre lease expires in eleven months and will not be renewed. The team plans to rehost about 300 virtual machines with no application changes. Which benefit is the one rehosting reliably delivers and therefore the one the plan should be justified on?
2 min answer -
intermediate Multiple choice
A nightly billing batch that ran in 4 hours 10 minutes on a 2016 on-premises server takes 9 hours 20 minutes after a lift-and-shift onto a cloud instance with twice the vCPUs and four times the memory. CPU sits near 12 percent across all cores and the instance is never network-throttled. Where is the time going?
3 min answer -
intermediate
An organisation rehosts its estate to cloud infrastructure and finds costs higher and reliability no better. What did rehosting not deliver, and what should follow?
2 min answer -
intermediate
When is lift-and-shift the right migration strategy, and what must be planned alongside it?
2 min answer
3 terms in this topic
Lift and Shift
Moving an application to new infrastructure with minimal change, trading optimisation for speed and low migration risk.
practiceMove Group
The set of workloads that must cross to the new infrastructure in the same wave because the round trips between them sit on a user-facing critical pa…
practiceRehost
Moving a workload to new infrastructure with no change to the application — fastest, cheapest to execute, and the source of the bill that discredits …
Neighbouring topics
Legacy Modernization
General material on modernising existing systems.
Legacy Assessment
Understanding what a system does before deciding what to do with it.
The Six Rs
Rehost, replatform, refactor, repurchase, retire, retain — per application.
Replatforming
Targeted changes that capture operational wins without a rewrite.
Refactoring & Re-architecting
Changing structure incrementally while the system keeps running.
Rebuild vs Re-architect
Why greenfield replacement fails, and the narrow cases where it does not.
Strangler Fig
Routing capabilities to new implementations behind a facade, one at a time.
Application Decomposition
Finding seams in a monolith, starting from the data.
Database Migration
Moving engines, versions and schemas without losing data or uptime.
Data Migration Strategies
Backfill, dual-write, reconciliation and verification.
Zero-Downtime Migration
Expand, migrate, contract — and the contract phase that never happens.
Parallel Run
Shadowing the old system to discover the rules nobody documented.
Cutover Planning
Rehearsals, go/no-go criteria and a rollback that has been executed.
Legacy Integration Patterns
Anti-corruption layers, adapters and CDC against systems that cannot change.
Mainframe Modernization
Batch windows, COBOL, and the risk profile of core banking systems.
Migration Risk
Bounding blast radius, staging by cohort, and honest readiness reporting.
Modernisation Business Case
Pricing tail risk so deferred maintenance becomes fundable.
Coexistence Patterns
Running old and new together for years without corrupting either.
Decommissioning
Actually switching the old system off, and proving nothing depended on it.