VM Migrations AWS <=> On-Premises

Application Discovery Service (AMS)

Allows us to discover on-premises infrastructure:
- What VM we have
- What CPU and memory they are allocated
- MAC addresses
- Resource utilization
- etc.
It also tracks these properties over time for more effective migration
AMS runs in 2 modes:
- Agentless (Application Discovery Agentless Connector):
  - It is an OVA based virtual appliance that integrates with VMWare
  - It can measure performance and resource usage, information which can be obtained from the outside of a VM
- Agent Based mode (with CloudWatch Agent): offers additional information from inside of a VM
  - Offers data gathering for network, processes, performance
  - We can see applications running on a VM
  - We can even see dependencies between VM based on network activity
AMS does not migrate anything, it helps us discover VM instances and relationships between them in order to be migrated
This information is valuable if we have thousands of instances we want to migrate
AMS integrates with AWS Migration Hub and Athena
AWS Migration Hub: tracks migrations of different types in AWS. Migrations such as VM migrations and database migrations

Server Migration Service (SMS)

Used to migrate whole VMs into AWS (including OS, Data, Apps, etc.)
This is the tool which actually performs the migration
It runs in agentless mode using a connector. The connector is VM which runs on on-premises within our existing VM environment
The connector integrates with VMware, Hyper-V and AzureVM
SMS does incremental replication of live volumes
Offers orchestration of multi-servers migrations
Creates AMIs which can be used to create EC2 instances
It can be used with other tooling such as CloudFormations to automate repeated deployment of instances
It too integrates with AWS Migration Hub

AWS Application Migration Service (MGN)

Is used to migrate servers from on-prem to AWS
It allows companies to lift-and-shift a large number of physical, virtual, or cloud servers without compatibility issues, performance disruption, or long cutover windows
AWS recommends agent-based replication when possible as it supports continuous data protection (CDP)
AWS MGN provides this agent. MGN creates a Launch Template which is then used to launch EC2 instances
AWS MGN provides a way to work out what kind of dependencies do we have between databases, app servers, web servers, etc. We can group these servers and migrate them together
It can also provide CloudFormation templates for deployment
Difference between SMS and MGN:
- Server Migration Service utilizes incremental, snapshot-based replication and enables cutover windows in hours
- Application Migration Service utilizes continuous, block-level replication and enables short cutover windows measured in minutes
AWS recommends to use MGN instead of SMS
We can migrate virtual and physical servers as well