# Adding Disaster Replica

A Disaster Recovery (DR) Replica is a cross-region, read-only copy of your Primary MySQL DB instance, designed to ensure high availability and business continuity in the event of a regional failure. It enables you to quickly recover operations in a different geographic region by maintaining a live replica of your data.

Tessell uses MySQL’s native Group Replication and extends it across regions to create a DR replica. Data from the primary DB instance is replicated asynchronously to the DR replica. Unlike a regular read replica, DR replicas are specifically designed for disaster recovery purposes, with support for manual failover and promotion workflows in the event of a regional outage.

The following diagram shows creating a DR Replica:

<figure><img src="/files/gtpU5wnaujYV2LAqjOOA" alt="" width="563"><figcaption></figcaption></figure>

***

### Prerequisites

Before creating a DR Replica, ensure the following:

* A MySQL DB service must already be provisioned.
* Every table in the database must have a primary key or an equivalent unique key (a requirement for MySQL Group Replication).
* Every table must use the InnoDB storage engine.
* The target destination region must be registered in Tessell Platform.

***

### Steps to Create a DR Replica

Follow the steps below to create a DR Replica using the Tessell Console:

1. Sign in to the Tessell Console.
2. From the left navigation pane, go to **DB Services** and open the **My Services** App.
3. Locate and select your MySQL DB service for which you want to create a DR replica.
4. Navigate to the **Instances** tab.
5. Click **Create Replica** in the right-hand pane, then select **Disaster Recovery** from the dropdown list.
6. Fill the required details:

   1. **Instance Name**: Specify a unique name for the read replica.
   2. **Region**: Select a different region from that of the primary DB instance.
   3. **Availability Zone**: Choose your preferred AZ within the selected region.
   4. **VPC/VNet**: Select the Virtual Private Cloud (VPC) or network.
   5. **Private Subnet**: Choose the subnet for the replica.

   <figure><img src="/files/uZDALIkO70WfXUDRSzhh" alt=""><figcaption></figcaption></figure>
7. Click **Add Instance** to start the replica creation process.

After the DR replica is successfully created, navigate back to the **Instances** page in the Tessell Console. The newly added instance appears in the list with the **Role** column indicating as **DR Replica**. In the event of a disaster, the DR replica can be promoted to take over as the new primary (manual action required).

***

### Limitations

* DR Replica can only be created after the MySQL DB service is provisioned.
* DR Replica must use the same compute shape as the primary DB instance.
* DR Replica must use the same parameter profile as the primary DB instance.
* DR Replica must use the same option profile as the primary DB instance.
* Failover to a DR replica is a manual operation through Tessell UI/API call (no auto-failover).


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.tessell.com/tessell/tessell-for-mysql/db-services/adding-disaster-replica.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.