docs/content/admin/monitoring-and-managing-your-instance/configuring-high-availability/creating-a-high-availability-replica.md

title, intro, redirect_from, versions, type, topics, shortTitle

title	intro	redirect_from	versions	type	topics	shortTitle
Creating a high availability replica	In an active/passive configuration, the replica appliance is a redundant copy of the primary appliance. If the primary appliance fails, high availability mode allows the replica to act as the primary appliance, allowing minimal service disruption.	/enterprise/admin/installation/creating-a-high-availability-replica /enterprise/admin/enterprise-management/creating-a-high-availability-replica /admin/enterprise-management/creating-a-high-availability-replica /admin/enterprise-management/configuring-high-availability/creating-a-high-availability-replica /admin/monitoring-managing-and-updating-your-instance/configuring-high-availability/creating-a-high-availability-replica	ghes *	how_to	Enterprise High availability Infrastructure	Create HA replica

{% data reusables.enterprise_installation.replica-limit %}

Creating a high availability replica

1. Set up a new {% data variables.product.prodname_ghe_server %} appliance on your desired platform. The replica appliance should mirror the primary appliance's CPU, RAM, and storage settings. We recommend that you install the replica appliance in an independent environment. The underlying hardware, software, and network components should be isolated from those of the primary appliance. If you are a using a cloud provider, use a separate region or zone. For more information, see AUTOTITLE.

2. Ensure that the new appliance can communicate with all other appliances in this high availability environment over ports 122/TCP and 1194/UDP. For more information, see AUTOTITLE.

3. In a browser, navigate to the new replica appliance's IP address and upload your {% data variables.product.prodname_enterprise %} license. {% data reusables.enterprise_installation.replica-steps %}

4. Connect to the replica appliance's IP address using SSH.

   ssh -p 122 admin@REPLICA_IP
   

{% data reusables.enterprise_installation.generate-replication-key-pair %} {% data reusables.enterprise_installation.add-ssh-key-to-primary %}

1. To verify the connection to the primary and enable replica mode for the new replica, run ghe-repl-setup again.

   ghe-repl-setup PRIMARY_IP
   

{% data reusables.enterprise_installation.replication-command %} {% data reusables.enterprise_installation.verify-replication-channel %}

Creating geo-replication replicas

This example configuration uses a primary and two replicas, which are located in three different geographic regions. While the three nodes can be in different networks, all nodes are required to be reachable from all the other nodes. At the minimum, the required administrative ports should be open to all the other nodes. For more information about the port requirements, see AUTOTITLE.

{% data reusables.enterprise_clustering.network-latency %} If latency is more than 70 milliseconds, we recommend cache replica nodes instead. For more information, see AUTOTITLE.

1. Create the first replica the same way you would for a standard two node configuration by running ghe-repl-setup on the first replica.

   (replica1)$ ghe-repl-setup PRIMARY_IP
   (replica1)$ ghe-repl-start
   

2. Create a second replica and use the ghe-repl-setup --add command. The --add flag prevents it from overwriting the existing replication configuration and adds the new replica to the configuration.

   (replica2)$ ghe-repl-setup --add PRIMARY_IP
   (replica2)$ ghe-repl-start
   

3. By default, replicas are configured to the same datacenter, and will now attempt to seed from an existing node in the same datacenter. Configure the replicas for different datacenters by setting a different value for the datacenter option. The specific values can be anything you would like as long as they are different from each other. Run the ghe-repl-node command on each node and specify the datacenter.

   On the primary:

   (primary)$ ghe-repl-node --datacenter [PRIMARY DC NAME]
   

   On the first replica:

   (replica1)$ ghe-repl-node --datacenter [FIRST REPLICA DC NAME]
   

   On the second replica:

   (replica2)$ ghe-repl-node --datacenter [SECOND REPLICA DC NAME]
   

   Tip

   You can set the --datacenter and --active options at the same time.

4. An active replica node will store copies of the appliance data and service end user requests. An inactive node will store copies of the appliance data but will be unable to service end user requests. Enable active mode using the --active flag or inactive mode using the --inactive flag.

   On the first replica:

   (replica1)$ ghe-repl-node --active
   

   On the second replica:

   (replica2)$ ghe-repl-node --active
   

5. To apply the configuration, use the ghe-config-apply command on the primary.

   (primary)$ ghe-config-apply
   

Configuring DNS for geo-replication

Configure Geo DNS using the IP addresses of the primary and replica nodes. You can also create a DNS CNAME for the primary node (e.g. primary.github.example.com) to access the primary node via SSH or to back it up via backup-utils.

For testing, you can add entries to the local workstation's hosts file (for example, /etc/hosts). These example entries will resolve requests for HOSTNAME to replica2. You can target specific hosts by commenting out different lines.

# <primary IP>      HOSTNAME
# <replica1 IP>     HOSTNAME
<replica2 IP>     HOSTNAME

Further reading

• AUTOTITLE
• AUTOTITLE