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blueprints/doc/source/caf/adopt/rehost.rst
Kyriakos Akriotis 8f13cc9a18 - CAF draft
2023-11-23 16:56:19 +01:00

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Rehost

Rehost, also known as lift and shift, is the most common way to migrate applications to the cloud without changing the running environment of applications. It is usually used for Physical to Virtual (P2V) and Virtual to Virtual (V2V) scenarios. It can help companies quickly migrate applications such as SAP, ERP, and CRM to the cloud.

Open Telekom Cloud provides three rehosting solutions:

Application redeployment

In this solution, applications can be redeployed on ECSs or BMSs. This solution is ideal for stateless applications that do not involve data migration. The OSs of cloud servers can be changed as needed, for example, if an old OS is no longer supported. This solution is recommended when a new OS is required, but this means the applications will be offline for a time.

Image import & export

By exporting system images of source servers and then importing those images to the cloud as private images, you can quickly create cloud servers with the same OSs and other details as your legacy servers. This solution is a good choice when you need to migrate on-premises servers that do not have too much data on them. The servers will have the same OSs before and after the migration, but there will be a fair bit of downtime.

Server Migration Service (SMS)

SMS can migrate applications to the cloud and synchronize incremental data to minimize the downtime. However, the OS cannot be upgraded during the migration.

Object Migration Method Pros and Cons
Virt ual/physical servers Redeployment
  • Easy OS change
  • Long downtime
Image import & export
  • OS consistency
  • Long downtime
SMS
  • OS consistency
  • Long downtime

Take a typical three-layer application architecture as an example. The following figure shows how the architecture is different before and after the migration.

image

Rehost has the following benefits:

  • The application architecture is consistent before and after the migration, so you know the original technology stack still work. Rehosting ensures the migration of your applications can go smoothly.
  • If the databases were built using Open Telekom Cloud ECS, the database licenses can be reused in commercial database scenarios to save money.
  • Applications are deployed across AZs, so you can configure DC-level HA.
  • With Open Telekom Cloud ELB and Auto Scaling, services can be flexibly scaled to adapt to workload changes.
  • ELB replaces traditional offline hardware load balancing devices and the network ACLs replace traditional hardware firewalls, further reducing the hardware investments required.
  • The O&M is simpler. CES provides comprehensive O&M monitoring of cloud infrastructure, and LTS provides quick collection and analysis of application logs.
  • The reliability is enhanced. CBR backs up cloud servers for restore or other server issues.
  • The security is hardened. HSS protects cloud servers, WAF filters web application traffic, and DBSS hardens cloud databases.