The core of cross-regional disaster recovery is to ensure business continuity through data replication and automatic switching. 1. Data replication methods include asynchronous replication (the best performance but may lose data), semi-synchronous replication (balanced consistency and availability) and group replication (high availability but high complexity), and are selected according to data tolerance; 2. Network latency and bandwidth affect replication efficiency, and it is recommended to compress transmission, merge transactions, and monitor delays; 3. The switching strategy is divided into manual and automatic. Automatic switching requires health checks and drills to avoid missed switching; 4. The multi-active architecture is a hot backup, which can be switched at any time but has high cost. Cold backup is suitable for non-core systems and has a long recovery time.

MySQL cross-regional disaster recovery is actually deploying database instances in different geographical regions to deal with regional failures or disasters. The core idea is to quickly switch traffic to the backup area when the main area is unavailable through data replication and automatic switching mechanisms, thereby ensuring business continuity.

1. Select data copy method

The key to cross-regional disaster recovery is how data is synchronized between different regions. Commonly used solutions are:

• Asynchronous Replication : The lowest latency, the best performance, but may lose data.
• Semisynchronous Replication : Receive logs at least one slave node before committing a transaction, balancing availability and consistency.
• Group Replication : Supports multi-write mode, suitable for high-availability scenarios, but has complex configuration and high resource consumption.

If you have low tolerance for data loss, it is recommended to give priority to semi-synchronous replication or group replication; if you value performance more and you can accept a small amount of data loss, then asynchronous replication is enough.

2. Network latency and bandwidth impact

Crossing regions often means higher network latency and limited bandwidth. This has a great impact on replication efficiency, especially for semi-synchronous and group replication.

Some optimization suggestions:

• Reduce bandwidth usage using compressed transfers (such as enabling binlog_compression )
• Avoid frequent small transaction submissions, appropriate merge operations to reduce the number of network interactions
• Monitor master-slave delay metrics (such as Seconds_Behind_Master ) to detect exceptions in a timely manner

If your master-slave nodes are deployed in East China and North China respectively, the delay may reach tens of milliseconds. At this time, asynchronous replication will be easier to maintain stability than semi-synchronous.

3. Switching strategies and automation

When there is really a problem in the main area, how can I quickly switch to the alternate node? There are two directions here:

• Manual switching : suitable for systems with low RTO (recovery time target) requirements, safe and controllable.
• Automatic switching : It requires cooperation with health checks, split brain detection and other mechanisms, such as using Orchestrator or MHA tools.

Some points to pay attention to when switching automatically:

• Don't switch because of short network jitter
• After switching, make sure that the data of the new master node is up to date.
• The application layer must also be able to perceive changes and update the connection address

It is generally recommended to do a complete drill first, simulate the main node downtime to see if the switch is normal, and don’t wait until something really happens to test it for the first time.

4. Multi-living architecture or cold-preparation?

There is another key decision in the disaster recovery plan: Are you planning to build a "hot backup" that is available at any time, or just put a cold backup and remain unmoved?

• Hot Standby : Real-time data synchronization, can be switched at any time, with high cost but low RTO/RPO.
• Cold Standby : The regular backup and recovery process is low but the recovery time is long.

If it is a financial system, you must choose hot backup or even multi-active architecture; for non-core businesses such as internal management systems, cold backup and script recovery is enough.

Basically that's it. Cross-regional disaster recovery is not something that can be achieved overnight. The plan must be determined based on business level, budget, and technical capabilities. The details that are easy to ignore include network fluctuation processing, DNS switching delay, permission configuration differences, etc., which are worth taking time to verify.

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