Does Your SQL Server Disaster Recovery Plan Stack Up?

In today’s data-driven world, having a robust disaster recovery (DR) plan is crucial for every business that relies on their data to keep the doors open. Unexpected failures, natural disasters, and human errors can strike at any time, putting your data and operations at risk.

In this article, we’ll explore key disaster recovery options in SQL Server, how to test these options, and why DR planning is essential to keeping your business running smoothly, even in the face of the unexpected.

Disaster Recovery Options in SQL Server

SQL Server offers a variety of native tools and technologies to ensure your data is protected and recoverable in case of disaster. Let’s break down the most used options:

Backups

At the core of any disaster recovery plan are backups. SQL Server provides full, differential, and transaction log backups to allow you to restore your database to a specific point in time. There are other, less frequently used backup types, but these are the most common.

· Full Backup: This is a complete copy of your database. Regular full backups ensure you always have a recent version of your entire dataset.

· Differential Backup: Captures only the data that has changed since the last full backup, providing a more space-efficient option while still reducing data loss.

· Transaction Log Backup: Records all changes made to the database and allows for point-in-time recovery, a critical part of a DR plan when you need to restore data with minimal loss.

Keeping these backups in a secure location, separate from the SQL Server that generated them is critical to being able to recover, especially in a ransomware event.

This is database level protection.

Log Shipping

Log shipping is a reliable DR option that involves automatically sending transaction log backups from the primary server to a secondary server at scheduled intervals. It allows you to have a warm standby, ready to take over if your primary server fails. This option is relatively simple to set up but may involve some data loss, depending on the frequency of log backups.

Log Shipping does not provide an automatic failover option. The secondary server can be used for reporting / read-only, but only between t-log restores.

This is at the database level.

Always On Availability Groups

SQL Server Availability Groups (AGs) offer a more advanced solution for disaster recovery and high availability. AGs replicate your databases to multiple secondary servers, called replicas, that can be configured for automatic or manual failover. In addition to DR, AGs also allow for load balancing of read-only queries across replicas, offering performance benefits in certain workloads.

AGs are available in Enterprise Edition SQL Server. Standard edition provides Basic Availability Groups, which are very limited in what they can do.

AGs provide database level protection.

Failover Clustering

SQL Server Failover Clustering Instances provide high availability at the instance level. It ensures that your SQL Server instance will automatically switch to another node in the cluster if the current node experiences hardware or software failure. This method ensures minimal downtime but may require more complex infrastructure and higher costs.

This is instance level. One downside is that there is only one copy of each database…the storage is shared between nodes.

Testing Your Disaster Recovery Plan

Even the best disaster recovery plan can fail if it hasn’t been rigorously tested. The only way to ensure your DR strategy is reliable is through regular testing.

Test Restore Your Backups

Regularly restore your full, differential, and transaction log backups to ensure they’re not corrupted and can be restored quickly in case of disaster. Document the recovery time and compare it to your Recovery Time Objective (RTO) to verify you can meet your business requirements.

This can be done manually, or automated through custom T-SQL, or tools such as Test-DbaLastBackup from the dbatools.io team.

Simulating Failovers

If you’re using Log Shipping, Availability Groups, or Failover Clustering, perform planned failovers to see how long the transition takes and to identify any issues. This will help you determine if your Recovery Point Objective (RPO) — the acceptable amount of data loss — is being met. Recovery Time Objective (RTO) is also tested here, although that is more of a High Availability topic than Disaster Recovery.

Run Real-World Disaster Simulations – for the truly bold!

To fully prepare for an actual disaster, simulate real-world scenarios like hardware failure, data corruption, or a complete site outage. Involving the entire team in the simulation can expose gaps in communication or process, ensuring you’re prepared for a worst-case scenario.

Do this during the day once you have successfully done it several times “off hours”. I dare you!

Document the Process

Testing should not only verify that your DR plan works, but it should also ensure that everyone involved understands their role. Document each step of your recovery process, including who is responsible for initiating recovery, what tools are needed, and the time expected for each task.

Each team member should have a current copy of the plan available to them at all times. Contact numbers / emails for each team should part of the plan.

The Bottom Line

Having a disaster recovery plan is a start, but ensuring it stacks up requires ongoing maintenance and testing. SQL Server provides a wealth of tools, from backups and log shipping to advanced solutions like Availability Groups, to protect your data and minimize downtime.

The key is not just having these options in place, but ensuring they are regularly tested and ready to go when disaster strikes. Take the time to review and test your SQL Server disaster recovery plan, and you’ll gain peace of mind knowing that your business is prepared to recover quickly, minimizing data loss and downtime.

The worst time to find out your DR plan doesn’t work is when you need it the most!

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