Replication performance errors

This topic covers replication errors related to performance, convergence, and lag in AWS Elastic Disaster Recovery.

Error: Replication not converging

Error: NOT_CONVERGING status

Cause: The rate of data changes on the source server exceeds the available replication bandwidth. Elastic Disaster Recovery cannot catch up with the ongoing writes.

Resolution:

Console

• Check Replication lag and ETA in the Elastic Disaster Recovery console.

• Check the Disk settings tab. Consider upgrading the staging disk type for higher throughput (for example, gp2 to gp3).

CLI

Run the following command to check replication lag and ETA:

aws drs describe-source-servers \
    --filters sourceServerIDs=SOURCE_SERVER_ID

Run the following command to check disk type, IOPS, and throughput configuration:

aws drs get-replication-configuration \
    --source-server-id SOURCE_SERVER_ID

Additionally:

• Calculate required bandwidth. For more information, see bandwidth requirements.

• Run a bandwidth test. For more information, see network bandwidth test.

Note

Changing the staging disk type might affect replication costs. Review Amazon EBS pricing before making changes.

Replication lag increasing

Symptom: Replication lag grows over time or spikes unexpectedly.

Causes:

• Source server is down or the agent is not running.

• TCP port 1500 is blocked outbound from the source server to the replication server.

• Source server MAC address changed. This requires agent reinstallation.

• Source server recently rebooted or Elastic Disaster Recovery services restarted. Disks are re-read, and lag grows temporarily until the process completes.

• Source server experienced a spike in write operations. Lag grows until Elastic Disaster Recovery flushes the backlog.

• Insufficient bandwidth for the combined write throughput of all source servers.

Resolution:

• Verify the agent is running and the source server is connected.

• Verify TCP port 1500 connectivity from the source server to the replication server.

• If the lag is temporary (post-reboot or write spike), wait for replication to converge.

• If lag persists, check bandwidth. For more information, see bandwidth requirements.

• Consider upgrading the staging disk type for higher throughput.

Error: Unknown data replication error

Error: unknown_error

Cause: An unclassified replication error. Multiple root causes are possible.

Resolution:

• Check connectivity between the source server and the replication server.

• Check AWS CloudTrail for API throttling errors.

• Monitor replication server performance (CPU, memory, disk I/O) in Amazon CloudWatch.

• Verify network bandwidth is adequate. For more information, see bandwidth requirements.

• Check agent logs. For more information, see Agent logs and diagnostics.

• If the error persists, contact AWS Support with the agent logs and source server ID.

Error: Failed to configure replication software

Error: FAILED_TO_CONFIGURE_REPLICATION_SOFTWARE

Cause: An internal error occurred during replication software configuration. This is typically transient.

Resolution: Retry the operation. If the error persists, contact AWS Support.

Error: Failed to download replication software

Error: FAILED_TO_DOWNLOAD_REPLICATION_SOFTWARE_TO_FAILBACK_CLIENT

Cause: The Failback Client cannot download replication software from Amazon S3. This indicates connectivity issues to the Amazon S3 endpoint, or a proxy or network security appliance is filtering traffic.

Resolution:

• Verify connectivity to the Amazon S3 endpoint. For more information, see TCP port 443 troubleshooting.

• Check for a proxy or network security appliance intercepting or blocking the download.

• Retry the operation.

Error: Failed to establish communication with recovery instance

Error: FAILED_TO_ESTABLISH_RECOVERY_INSTANCE_COMMUNICATION

Cause: The Failback Client cannot communicate with the recovery instance.

Resolution:

• If you use a public network (no VPN or ), ensure the recovery instance has a public IP address. By default, Elastic Disaster Recovery launch templates disable public IP assignment.

• If you use a private network, verify routing between the Failback Client and the recovery instance.

• Check that the security group on the recovery instance allows inbound traffic on the required ports.

Error: Failed to pair replication agent with replication server

Error: Failed to pair replication agent with replication server

Cause: The replication agent, replication server, and Elastic Disaster Recovery endpoint cannot establish a three-way communication channel.

Resolution:

• Verify connectivity between the agent, the replication server, and the Elastic Disaster Recovery endpoint.

• If the error persists, contact AWS Support.