Add Extra Volume

  1. Create EKS cluster with 3 nodes and install Longhorn.
  2. Create deployment and write some data to it.
  3. In Longhorn, set replica-replenishment-wait-interval to 0.
  4. Go to the launch template of the EKS cluster node-group. You can find in the EKS cluster tab Configuration/Compute/<node-group-name> and click the launch template.
  5. Click Modify template (Create new version) in the Actions drop-down menu.
  6. Choose the Source template version in the Launch template name and version description.
  7. Click Advanced then Add new volume in Configure storage and fill in the fields.
  8. Adjust the auto-mount script and add to User data in Advanced details. Make sure the DEV_PATH matches the Device name of the additional volume. 
    MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="==MYBOUNDARY=="
--==MYBOUNDARY==
Content-Type: text/x-shellscript; charset="us-ascii"
#!/bin/bash
# https://docs.aws.amazon.com/eks/latest/userguide/launch-templates.html#launch-template-user-data
echo "Running custom user data script"
DEV_PATH="/dev/sdb"
mkfs -t ext4 ${DEV_PATH}
MOUNT_PATH="/mnt/longhorn"
mkdir ${MOUNT_PATH}
mount ${DEV_PATH} ${MOUNT_PATH}
  9. Click Create template version to save changes.
  10. Go to the EKS cluster node-group and change Launch template version in Node Group configuration. Track the status in the Update history tab.
  11. After update succeeded, check the deployment in step 2 still running and data exist, and check the extra volume can be added through Longhorn UI.
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