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Cloud Backup:Cross-zone disaster recovery

Last Updated:Feb 26, 2024

If a production site encounters force majeure events such as a fire or power outage, or equipment failures such as a software or hardware failure, your application may fail to run for a short period of time. To ensure business continuity, you can use the Elastic Compute Service (ECS) disaster recovery feature to back up the application across zones. This prevents faults that may occur in a single zone and meets the recovery point objective (RPO) and recovery time objective (RTO) goals of your business.

Before you begin

Select a zone to deploy the disaster recovery system. Create a virtual private cloud (VPC) in the zone. Create a vSwitch for replication and a vSwitch for restoration in the VPC.

Step 1: Create a disaster recovery site pair

To create a disaster recovery site pair that provides cross-zone disaster recovery protection for ECS instances at the production site, perform the following steps:

  1. Log on to the Cloud Backup console.

  2. In the left-side navigation pane, choose Disaster Recovery > ECS Disaster Recovery.

  3. In the upper-right corner of the Disaster Recovery Center page, click + Add.

  4. In the Create Site Pair panel, select Cross-zone Disaster Recovery for Type and select the VPC that is created for the production site.

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  5. Click Create.

Step 2: Add the ECS instances to be protected

To add the ECS instances to be protected, perform the following steps:

  1. Click the Protected Server tab. In the upper-right corner of the tab, select the disaster recovery site pair that you created in Step 1 from the drop-down list.

  2. On the Protected Server tab, click + Add. Select the ECS instances and click OK.

    You can select 1 to 10 ECS instances.

    In the Server Status column, the status of the added ECS instances is Agent Installing and then changes to Initialized. If the status of an ECS instance is not Initialized, choose More > Server Operation > Restart Server in the Operation column to initialize the instance.

Step 3: Start replication

To enable real-time replication of ECS instances to Alibaba Cloud, perform the following steps:

  1. On the Protected Server tab, find the ECS instance that you want to replicate and choose More > Failover > Start Replication in the Operation column.

  2. On the Enable Replication panel, set the parameters and click Start.

    Parameter

    Description

    Recovery Point Policy

    Select the interval at which recovery points are created from the drop-down list. Unit: hours. For example, if you select 1 hour, Cloud Backup creates a recovery point every hour.

    Use SSD

    Specify whether to use SSD. If you select this check box, SSDs are used for replication. If you use SSDs, the I/O performance of the ECS instance on the cloud after server migration or failover is significantly improved. However, the usage cost increases. We recommend that you select as needed.

    Replication Network

    Select a replication network from the drop-down list. Cloud Backup uses this network to replicate disaster recovery data to the cloud.

    By default, Cloud Backup reads the available vSwitches of the secondary VPC network. If the replication network and the recovery network share the same vSwitch, data can be restored with higher speed. If the replication network and the recovery network are not in the same zone, the RTO becomes longer. We recommend that you configure the same zone for the replication network and the recovery network.

    Recovery Network

    Select a recovery network from the drop-down list. During disaster recovery, Cloud Backup uses this network to restore disaster recovery data. For example, Cloud Backup uses this network to create an ECS instance during a disaster recovery drill or failover.

    By default, Cloud Backup reads the available vSwitches of the secondary VPC network. If the replication network and the recovery network share the same vSwitch, data can be restored with higher speed. If the replication network and the recovery network are not in the same zone, the RTO becomes longer. We recommend that you configure the same zone for the replication network and the recovery network.

    Automatic restart after replication interruption

    Specify whether to automatically resume replication if an interruption occurs.

    The ECS instance then enters the Enable Replicating, Initial Full Sync, and Replicating states in sequence.

    1. Enable Replicating: ECS disaster recovery is scanning data on the ECS instance and evaluating the overall data volume. In most cases, this process takes a few minutes.

    2. Initial Full Sync: ECS disaster recovery is replicating valid data on the ECS instance to Alibaba Cloud. The replication duration depends on factors such as the data volume and the network bandwidth of the ECS instance. The progress bar in the Server Status column shows the replication progress.

    3. Replicating: After all valid data on the ECS instance is replicated to Alibaba Cloud, Aliyun Replication Service (AReS) monitors all write operations that are performed on the disks of the ECS instance and replicates the incremental data to Alibaba Cloud in real time.

(Optional) Perform a disaster recovery drill

After an ECS instance enters the Replicating state, you can perform a disaster recovery drill on the ECS instance.

A disaster recovery drill is an important part of disaster recovery. It allows you to run a protected ECS instance on the cloud to verify whether your applications can run as expected. A disaster recovery drill has the following features:

  • Allows you to easily check whether an application can run on a restored ECS instance as expected.

  • Familiarizes you with the disaster recovery process and makes sure that a smooth failover can be performed when the primary site encounters a failure.

To perform a disaster recovery drill, perform the following steps:

  1. On the Protected Server tab, find the ECS instance and click Test Failover in the Operation column.

  2. On the Test Failover panel, set the Recovery Network, IP Address, Use ECS Specification, Hard Disk Type, Recovery Point, Elastic Public Network IP, and Post Script parameters. Then, click Start.

    Note
    • Cloud Backup automatically retains 24 recovery points that are created in the most recent 24 hours for each ECS instance.

    • If you do not select Use ECS Specification, you must set the CPU and Memory parameters.

    Alibaba Cloud then runs the application on a restored ECS instance at the specified time. The disaster recovery drill does not affect real-time data replication.

    After the disaster recovery drill is completed within a few minutes, click the link in the Test Failover Information column to verify restored data and applications.

  3. Clear the drill environment.

    After the verification is completed, click Cleanup Test Environment in the Operation column. Then, the restored ECS instance is deleted.

    Note

    After the restored ECS instance is verified, we recommend that you delete the restored ECS instance at the earliest opportunity to reduce costs.

Step 4: Perform a failover

Regular disaster recovery drills ensure that you can run your applications on restored ECS instances at any time. When a critical error occurs in the primary site, you can switch your workloads to the secondary site.

Warning

Failover is applicable to protected ECS instances where a critical error occurs. During the failover, ECS disaster recovery stops real-time data replication. To resume replication for a protected ECS instance, you must choose More > Server Operation > Restart Replication in the Operation column.

To perform a failover, perform the following steps:

  1. On the Protected Server tab, find the ECS instance and choose More > Failover > Failover in the Operation column.

  2. On the Failover panel, set the Recovery Network, IP Address, Use ECS Specification, Hard Disk Type, Recovery Point, Elastic Public Network IP, and Post Script parameters. Then, click Start.

    Important

    You can restore the ECS instance to the current point in time only once.

  3. After the failover is completed, click the link in the Recovered Instance ID/Name column to verify restored data and applications.

    • If the applications run as expected after being restored to the current point in time, choose More > Failover > Commit Failover in the Operation column.

      Note

      After you complete the failover or change the recovery point and verify that applications restored from the protected ECS instance are running your business, you can commit the failover to release the cloud resources that are occupied during failover to save resources.

    • If the applications do not meet the requirements after being restored to the current point in time, for example, data in the restored database is inconsistent with that in the source database or dirty data on the source ECS instance is synchronized to the restored ECS instance in the destination region, choose More > Failover > Change Recovery Point in the Operation column to change the recovery point before you commit the failover.

    Note

    The procedure for changing the recovery point is similar to that for failover, except that you must select a recovery point earlier than the current point in time.

Step 5: Perform a reverse replication

After you replicate applications on a protected ECS instance in Zone A to Zone B, you can also perform reverse replication to replicate applications from Zone B to Zone A.

To perform a reverse replication, perform the following steps:

  1. On the Protected Server tab, find the ECS instance and choose More > Failback > Reversed Register in the Operation column. In the message that appears, confirm that you want to perform a reverse registration on the ECS instance.

  2. In the Actions column, choose More > Restore > Initiate Reverse Replication.

  3. On the Initiate Reverse Replication panel, set the Original machine recovery, Replication Network, and Recovery Network parameters. Then, click Start.

    Warning

    Cross-region disaster recovery and cross-zone disaster recovery allow you to replicate applications back to the original ECS instance. However, when you replicate applications back to the original ECS instance, data on the original ECS instance is overwritten. Perform this operation with caution.

  4. After the ECS instance enters the Reversed Enable Replicating state, choose More > Failback > Failback in the Operation column.

  5. On the Failback panel, set the CPU, Memory, Recovery Network, IP Address, and Post Script parameters. Then, click Start.

  6. After the failback is completed, choose More > Failover > Registration in the Operation column to register the protected ECS instance again.