SQL Server High Availability and Disaster Recovery Explained

What Is High Availability and Disaster Recovery?

This section introduces the basic meaning of SQL Server HA and DA. Both the elements are important in its own way. The failure of one can create several problems in the database. So, it is mandatory to plan a strong SQL Server disaster recovery plan to get the data back. Else, go with the automated SQL Server Database Recovery Software. Now, let us understand HA and DA in a brief manner.

• High Availability or HA
  In the IT domain, HA refers to a component that is highly available and continuously operational. The advantage of SQL Server 2012 high availability is if one system goes down, another one is ready for work. This solution overcomes the downsides of hardware or software breakdown/failure. Also, it can proficiently manage the availability of resources so that the downtime loss can be minimized.
• Disaster Recovery Plan
  Disaster Recovery strategies are those that can repress data loss situation after any disaster in SQL Server. An HA system works is to make the resources available for data. However, it does not tell the processed data is correct or not. Let us consider a situation where a database Administrator forgets to write ‘Where’ in the Update statement. By doing this, the table gets blanked suddenly. In such a scenario, the high-availability system does not work. In fact, it makes the situation worse as it creates the duplicate of bad data to other sites. So, it is always advised to have a well documented SQL Server 2012 disaster recovery plan that is shared with the reliable person.

How Can We Achieve SQL Server High Availability and Disaster Recovery Solutions?

Basically, there are different ways through which users can reach HA and DR solutions. All of them are enlisted below.

1. Failover Cluster Instance
2. Log Shipping
3. Database Mirroring
4. Replication
5. Backup
6. Physical Redundancy

Many users used the Failover Cluster, Log Shipping, or Database Mirroring feature to accomplish HA and DR before the release of SQL Server 2012 high availability and disaster recovery. But, the users are not satisfied with these options and requested more feature to attain high availability and disaster recovery solutions. The customer requirement was better availability, higher return on investment (ROI), and less complex features. Because the existing model has some limitation and all are listed below.

Improve SQL Server High Availability and Disaster Recovery

• Clustering
  This feature is only designed to provide data protection against server failure. In the case of SAN breakdown, it goes down and does not prevent data loss. That is why it is not suitable for a disaster recovery plan.
• Data Replication
  With this feature, the server does not retain the complete copy of a database. Only a few objects such as tables, views etc. can be published. So, we cannot say that the secondary server has a similar database same as primary one. Certainly, it is not a best HA solution.
• Log Shipping
  SQL Server Log Shipping feature is used for disaster recovery purpose. It permits the users to automatically send transaction log backups from the primary server database to a secondary server database. Furthermore, an optional Monitor Server track the history & status of backup and restore operations. It also generates alerts if these operations go down as scheduled.
• Database Mirroring
  It is a solution used for enhances the database of SQL Server high availability. Moreover, it is executed on a single database. Also, it can only implement on those databases that use the full recovery mode.
• Advanced Solutions
  Users can trust the SQL Server Recovery Manager solution as well to get  a complete protection against severe threats to SQL database. Also, these tools help users in analyzing the data in SQL with ease.

All the limitation of HA and DR model has removed in SQL Server 2012 high availability and disaster recovery solutions. They introduce the AlwaysOn feature that overcomes all the flaws of the previous model.

Striking Features of AlwaysOn

In SQL Server AlwaysOn, a user does need to keep eye on a server. It has robust technology that makes it capable to switch between automatic failover from primary database to a secondary database.

• Provide a great number of the secondary server.
• Able to read the secondary database.
• Provide high availability management
• Automatic Multiple Database failovers

Summing Up

No matter how a user plans risk management, the most crucial element is data loss. An organization may suffer huge harm when data loss situation occurs. Therefore, in this article, we have provided enough knowledge about SQL Server High Availability and Disaster Recovery solutions. In case, the data become highly corrupted and cannot be recovered, then you can go with the third-party SQL Recovery software.