AWS Application Migration Service

What it is

AWS Application Migration Service, now called AWS Transform MGN (MGN), automates the migration of physical, virtual, and cloud servers to AWS with minimal downtime, typically cutover windows of minutes. It continuously replicates your source servers at the block level and converts them to run natively on AWS, so you can move large numbers of servers without compatibility problems. It supports Windows Server and many Linux distributions.

The exam still uses the name Application Migration Service. Choose it when a question asks to lift and shift (rehost) servers or VM (Virtual machine)A software computer that runs its own operating system on shared physical hardware, kept apart from other VMs by a hypervisor. An EC2 instance is a VM, except bare metal instances.Glossary entry to EC2 quickly, with minimal changes and downtime. After the move, you can replatform or refactor applications as a next step.

How it works

Install the AWS Replication Agent on each source server. For VMware vCenter, you can also use agentless snapshot replication with the MGN vCenter Client.
MGN continuously replicates the server's disks to a staging area in your AWS account, so the copy stays current.
Launch test instances to check that the servers work on AWS, without affecting the source.
When ready, launch cutover instances. Because replication is continuous, the final switch takes minutes.
When the cutover is complete, replication is disconnected and you mark the source servers as archived.

Templates and scale

Three configurable templates control each server:
- Replication template: how data is replicated.
- Launch template: how instances are launched.
- Post-launch template: actions to run after launch.
Template settings apply to new servers, and you can override them per server.
Group servers into applications, and applications into waves, to launch, cut over, and archive in bulk.
You can replicate into standard AZ (Availability Zone)An isolated location within an AWS Region, made up of one or more data centers with their own power, cooling, and networking. The AZs in a Region are linked by fast, low-latency connections, so spreading resources across them protects against the failure of one site.Glossary entry or Local Zones.
Replication uses all available bandwidth by default. On a shared link, set Throttle bandwidth (per server, in Mbps) in the replication settings so that users keep enough capacity.

Security and cost

All communication is encrypted with TLS (Transport Layer Security)The protocol that encrypts traffic between a client and a server and lets the server prove its identity with a certificate. It replaced SSL, though the older name is still common; HTTPS is HTTP over TLS.Glossary entry, and the staging area (replication servers and staging disks) and the launched instances live in your own account and VPC.
By default, source servers send replicated data to the replication servers' public IP (Internet Protocol)The protocol that addresses and routes packets between networks. Each device has an IP address: IPv4 addresses look like 192.0.2.1, and IPv6 addresses are longer, like 2001:db8::1.Glossary entry addresses over the internet. To keep it off the internet, choose Use private IP in the replication settings, which routes the data over an existing Direct Connect, VPN (Virtual private network)An encrypted tunnel over a public network, such as the internet, that joins networks or devices as if they were directly connected. AWS Site-to-Site VPN connects networks; AWS Client VPN connects individual users.Glossary entry, or VPC peering connection. MGN does not create that connection.
Pricing: the first 90 days (2,160 hours) of replication per server are free; after that, there is an hourly charge per server. You also pay for the staging and launched AWS resources.

Application Migration Service or another option?

If the requirement is	Choose
Rehost physical, virtual, or cloud servers to EC2 with minimal downtime	AWS Application Migration Service (AWS Transform MGN)
Migrate a database, possibly to another engine	AWS DMS
Copy file shares to S3, EFS, or FSx	AWS DataSync
Run VMware workloads on AWS without converting them	Amazon EVS
Ongoing DR (Disaster recovery)Preparing for and recovering from events that take a workload down, such as a Regional outage or deleted data. AWS describes four strategies, from cheapest and slowest to costliest and fastest: backup and restore, pilot light, warm standby, and multi-site active/active.Glossary entry of servers to AWS	AWS Elastic Disaster Recovery

Reverse mindmap: when the question points here

Is it Application Migration Service?

Yes, when the question says
- Lift and shift servers to AWS leads to Application Migration Service
- Rehost many VMs with minimal downtime leads to Application Migration Service
- Physical, VMware, or other-cloud servers to EC2 leads to Application Migration Service
Know how it works
- Keep the copy current until cutover leads to Continuous block-level replication
- No agent on VMware servers leads to Agentless vCenter replication
- Check servers before switching leads to Test launch
- Move groups of servers together leads to Applications and waves
- Replication must not cross the internet leads to Use private IP over Direct Connect or VPN
- Replication saturates a shared link leads to Throttle bandwidth per server
No, when the question says
- Migrate only the database leads to DMS
- Copy files leads to DataSync

Key takeaways

Application Migration Service (now AWS Transform MGN) rehosts servers to AWS with cutover windows of minutes.
It replicates source servers continuously at the block level, with an agent or agentless on vCenter.
Test launches validate servers before cutover; replication, launch, and post-launch templates standardize settings.
Applications and waves let you migrate large estates in bulk.
Replication goes over the internet by default; Use private IP sends it over Direct Connect, VPN, or peering, and ThrottlingLimiting how many requests a client can make in a period. A throttled request is rejected, often with HTTP status 429 or a throttling error, and should be retried later with backoff.Glossary entry caps its bandwidth.
Replication is free for the first 90 days per server.