Online Backup with Emic Application Cluster

You do not have to be a topnotch DBA to understand the need of the proper database backup and restorination procedures. Even when you have adopted a high availability solution like a clustered database system in order keep your database up and running - backup is still needed.

Depending on your service availability and other database availability requirements, the database backup procedure may present its own challenges and may require special planning and specific tools as well.

As long as your Emic application cluster (EAC) contains three or more nodes, you can make online backups without causing any application downtime. In the following section, we describe how online backup can be done on a production system with EAC, without blocking client access to database service and while still insuring no single-point-of-failures.

Imagine that you have a three nodes in your EAC cluster: MySQL A, MySQL B and MySQL C, all nodes are running in online mode, accepting a client connections and having fully synchronized databases.

Do the following:

Step 1. Set one of the nodes e.g. MySQL node C, to the 'offline' via the cluster manager or GUI user interface. EAC will make sure that this offline process happens gracefully i.e. all current connections are allowed to complete their processing, but no new connections are allowed.

Step 2. Perform a normal backup process in MySQL node C by using your favorite backup tools and techniques.

Step 3. Restore the MySQL node C back to the cluster, setting it back to the online state via the cluster manager user interface or GUI.

In Step 3, where the node is set back to the online state, the system automatically initiates a snapshot replication protocol by selecting an online node (e.g. MySQL B) and updates its database by copying all tables from MySQL node B. Before this initial snapshot replication starts, MySQL node B stops accepting new client connections and goes gracefully to standby state. During the snapshot replication, both MySQL B and MySQL C continue to be synchronized by MySQL A, and when they are finished they apply a new changes in their database and turns to active. At this point, the database state of all three nodes is synchronized.

Congratulations! You have successfully performed a true high-availability online backup of your database with no impact on client requests. EAC for MySQL not only provides an online backup capability, but also offers:
i) dynamic load balancing
ii) fault management with fast failovers
iii) high availability, and
iv) performance scalability with each added server node

For more information about EAC for MySQL, visit
http://www.emicnetworks.com