Agent related

This section contains answers to questions about the AWS Replication Agent.

What does the AWS Replication Agent do?

The AWS Replication Agent performs an initial block-level read of the content of any volume attached to the server and replicates it to the replication server. The agent then acts as an OS-level read filter to capture writes and synchronizes any block level modifications to the AWS Application Migration Service replication server, ensuring near-zero RPO.

What kind of data is transferred between the agent and the AWS Application Migration Service?

The AWS Replication Agent sends the following types of information to the Service Manager of AWS Application Migration Service:

When an Agent is installed on a source server, it collects the following information on the machine:

Can a proxy server be used between the source server and the AWS Application Migration Service console?

Yes. The proxy is configured using an environment variable prior to the install.

https_proxy=https://PROXY:PORT/

For example: https_proxy=https://10.0.0.1:8088/

Make sure the proxy has a trailing forward slash.

Ensure that you have allowlisted the MGN IPs and URLs for both SSL Interception and Authentication.

What are the prerequisites needed to install the AWS Replication Agent?

The installation requirements for source server depend on the type of OS that the server runs – either Linux or Windows.

Prerequisites can be found here.

What ports does the AWS Replication Agent utilize?

The Agent utilizes TCP Port 443 to communicate with the Service Manager of Application Migration Service and TCP Port 1500 for replication to AWS.

What privileges does the AWS Replication Agent require?

The AWS Replication Agent installer requires root privileges or the use of the sudo command during installation. It creates an "aws-replication" group and user, and attempts to add the "aws-replication" user to the "sudoers" file to grant necessary permissions. Ensure that the user running the installation has sufficient privileges to modify the "sudoers" file. If the installation fails due to insufficient permissions, you may need to manually add the "aws-replication" user to the "sudoers" file before attempting the installation again.

Is it possible to install the agent on servers running operating systems that are not listed as supported?

The agent is designed and tested to work on the officially supported operating systems listed in the documentation. Installing the agent on other unsupported operating systems may be possible but is not recommended. Any installation or replication issues encountered when using unsupported operating systems will need to be handled through your own troubleshooting or support channels, as the AWS engineering team will be limited in their ability to assist. We advise using the agent only on supported OS versions to ensure the best experience. Please refer to the documentation for the list of supported operating systems before installation.

What kind of resources does the AWS Replication Agent utilize?

The AWS Replication Agent is lightweight and nondisruptive. The agent utilizes approximately 5% CPU and 250 MB of RAM.

Can AWS Application Migration Service migrate containers?

AWS Application Migration Service (AWS MGN) only supports the replication of full servers. Nevertheless, AWS MGN replicates on a server level and therefore any containers within the selected servers will be replicated.

Does the AWS Replication Agent cache any data to disk?

AWS Application Migration Service does not write any cache or do any sort of journalling to disk. The Agent holds a buffer which is large enough to map all volume's blocks ~250 MB in memory.

The agent then acts as a sort of write filter and will replicate changed blocks directly from memory to the Replication Server. In cases where the data is no longer in memory, the agent will read the block from the volume directly. This is the case where you may see backlog in the AWS Application Migration Service console. The cause of this is the volume of change is greater than the bandwidth available.

How is communication between the AWS Replication Agent and the AWS Application Migration Service secured?

All communication is encrypted using SSL. In addition, each Agent is assigned a key during installation which is used to encrypt all traffic. All keys are unique and are not shared across multiple agents.

Is it possible to change the port the AWS Replication Agent utilizes from TCP Port 1500 to a different port?

No. The AWS Application Migration Service Agent can only utilize TCP Port 1500 for replication.

How do I manually uninstall the AWS Application Migration Service agent from a server?

Follow the steps in the Uninstalling the Agent section.

When do I need to reinstall the agent?

Typically, you need to reinstall the Agent after any major upgrade to the source server.

Linux

Windows

How much bandwidth does the AWS Replication Agent consume?

The AWS Replication Agent opens up to five connections and will attempt to maximize available bandwidth.

Throttling can be activated via the AWS Application Migration Service console by either selecting a specific server and clicking the Replication settings tab or by changing the Replication template (in this case the change will only affect newly added servers).

How many disks can the AWS Replication Agent replicate?

The agent can replicate up to 63 disks from a single server.

Is it possible to add a disk to replication without a complete resync of any disks that have already been replicated?

When you are adding a disk to a source server, AWS Application Migration Service will not automatically identify this disk and add it to the Disk settings section in the console.

The only way to get this disk to replicate is to reinstall the agent. Before reinstalling, you can note the current Total replicated storage. When you reinstall the agent, you will notice the value of replicated storage changes.

You will also notice an additional progress bar appear, which indicates that we are rescanning the original volumes. This is not a resync, but a scan, to verify that all the blocks on the source still match the blocks on the replication side. This process is significantly quicker than a resync, as there is no actual block data transferred, unless there is a difference. This is needed, as a reinstall results in the driver which performs the IO tracking being unloaded and reset, so we have no way of being certain of the sync status. Whilst the rescan on the original volumes is happening, the agent is also ensuring that the initial sync of the new volume is being completed in parallel.

Is the AWS Replication Agent installed on launched test and cutover instances?

During the launch process, either upon test or cutover instance launch, the AWS Replication agent is removed from the test or cutover instance, and will not run on it.

How do temporary credentials work?

The temporary credential mechanism was developed specifically to provide an easy and secure way to install AWS MGN Agents. The main flow of the temporary credentials' creation process relies on generating an x509 certificate per agent and then using this x509 certificate to receive temporary IAM credentials. This process utilizes a similar mechanism to the one used by IAM Roles Anywhere.

Which Windows and Linux OSs support no-rescan upon reboot?

A shutdown (from the OS menu or CLI) of any supported Linux or Windows source server no longer causes a rescan in AWS MGN once the source server is restarted.

A rescan means that the agent on the source server rereads all blocks on all replicated disks and transmits blocks that are different from the previously replicated data. A rescan is similar to the initial sync but is faster because only blocks that are different need to be transmitted.

Rescans can still happen following a hard reboot, crashes, or when you add or remove disks to or from the source server.

Supported OSs include:

Windows Server

Linux