Disaster recovery (DR) refers to the strategies and plans in place to restore IT infrastructure and capabilities after a disruptive event like a cyberattack, natural disaster, or system failure. Having a comprehensive disaster recovery plan is crucial for any organization relying on digital systems and data storage. According to research, 93% of companies without a disaster recovery plan go out of business within one year of a major data loss event.
A disaster recovery plan outlines the policies, procedures, and technical strategies needed to recover critical systems, applications, and data. The goal is to restore normal operations as quickly as possible after a disruption. Disaster recovery planning involves prevention, preparedness, response, and recovery. Key elements of a DR plan include backups, replication, alternative sites, and emergency response procedures.
This article will provide an overview of the main database disaster recovery strategies and best practices that organizations should have in place to mitigate risk and downtime.
Prevention
Preventing disasters before they occur is a critical first step in database disaster recovery. Some key prevention strategies include:
Implementing a comprehensive backup plan that includes frequent backups to both local and offsite locations. Best practices recommend daily incremental backups along with weekly full backups. Backups should be automated and monitored.
Using data replication to maintain a live copy of production data at a secondary site. This enables rapid failover if the primary database goes down.
Having redundant infrastructure like RAID disk arrays and clustered servers. This provides high availability and seamless failover in case of hardware failures.
Following infrastructure best practices like virtualization, SAN storage, and high-performance networking between sites. These technologies help minimize downtime during outages.
Monitoring system health proactively with automated alerts. This enables catching issues early before they cause major outages.
Data Replication
Data replication is the process of copying and distributing data from one database to another. It ensures availability and consistency between source and target databases. There are two main types of data replication: synchronous and asynchronous.
Synchronous data replication means that data is copied and written simultaneously to the source and target databases. Any changes made to the source database are instantly replicated to the target in real-time. This ensures strong consistency as the source and target databases are identical at all times. However, synchronous replication can impact performance as every transaction must be completed on both databases before the next one can start (Source).
Asynchronous data replication copies data from the source database to the target database after a delay. Transactions are first applied to the source database before being replicated to the target. This improves performance compared to synchronous replication. However, there is a risk of data loss if the source database fails before changes can be replicated. The target database may also be slightly out-of-date compared to the source (Source).
Overall, synchronous replication prioritizes strong consistency while asynchronous replication favors better performance. The optimal method depends on the specific needs and priorities of the system.
Backups
Backups are critical for protecting databases against data loss and corruption. There are several types of database backups:
- Full backups – A full backup copies the entire database and transaction log files. This provides a complete restore point, but takes the longest to perform. Full backups are usually run weekly or monthly. (Source)
- Incremental backups – An incremental backup only copies data that has changed since the last full or incremental backup. This makes them faster than full backups, but requires access to other backups for a full restore. Incremental backups are usually run daily. (https://www.techtarget.com/searchdatabackup/feature/Full-incremental-or-differential-How-to-choose-the-correct-backup-type)
- Differential backups – A differential backup saves all changes made since the last full backup. It allows restore from just the most recent full and differential backups. Differentials provide a balance of backup speed and restore convenience. (Source)
The type of backup strategy depends on the specific needs of an organization. For example, businesses with large databases may prefer more frequent incremental backups, while others do weekly full and daily differential backups for efficiency. Testing and validating backups is critical to ensure the recovery process works when needed.
Secondary Failover Sites
Having a secondary failover site is a critical component of a disaster recovery strategy. The secondary site acts as a redundant copy of the primary production site that can be activated in the event of an outage or disaster. There are several advantages and potential drawbacks to having a secondary failover site:
Advantages:
- Allows for continuous availability – With a secondary site ready to take over, downtime can be minimized in a disaster scenario
- Protection against data loss – Data can be replicated from the primary site to keep the secondary up-to-date
- Reduced recovery time – Failover to the secondary site can be automated for rapid disaster recovery
- Flexibility – Secondary site can also be used for testing, analytics, reporting etc.
- Compliance – Having a resilient DR infrastructure may be required for regulatory compliance
Potential drawbacks:
- Complexity – Requires careful planning, testing, and maintenance of the secondary site
- Cost – Maintaining redundant infrastructure incurs additional costs
- Data synchronization – There may be some data loss if replication to the secondary is not fully in sync
- Distance – Greater physical distance introduces latency in failover scenarios
- Testing – Comprehensive disaster testing requires taking primary application offline
Overall, a secondary failover site is considered an essential strategy for minimizing downtime during catastrophic outages, despite the complexity and costs involved. The advantages generally outweigh the drawbacks for mission-critical systems.
Emergency Procedures
Having established emergency procedures in place is a critical component of any disaster recovery plan. As IBM notes, these procedures document the appropriate response to disasters in order to protect resources and resume operations. They outline the steps to take during an emergency event.
Emergency procedures should identify roles and responsibilities, detailing who gets notified and who authorizes the activation of recovery plans. They stipulate the sequence of recovery actions, such as failover to alternate sites. Procedures should also establish recovery time objectives that set goals for restoration of critical systems and data within a designated timeframe.
For example, a company may set a recovery time objective of 4 hours for restoring core databases after an outage. Their emergency procedures would then outline the coordinated steps between teams to recover database backups and switch to alternate servers within that 4 hour window.
Having clear, documented emergency procedures gives an organization the ability to respond swiftly and effectively when disaster strikes. Following established procedures reduces chaos, ensures proper notifications, and facilitates a timely return to normal operations.
Testing
Regular testing of disaster recovery plans is crucial to ensure that recovery strategies will work when needed. Disaster recovery testing validates the technical components and procedures in a plan while also training staff who participate in the test. Some key reasons for regular disaster recovery testing include:
- Confirm recovery technologies and strategies are implemented and functioning
- Identify gaps, inconsistencies, or areas for improvement in the plan
- Demonstrate the feasibility of the plan to management
- Fulfill compliance requirements for regulated industries
- Provide hands-on experience for disaster recovery teams
According to industry best practices, disaster recovery testing should be conducted at least annually. The most comprehensive form of testing is a full failover test which simulates a real disaster scenario and activates the recovery site. However, tabletop exercises, dependency analysis, and component testing are also important for ongoing validation.
Regular disaster recovery testing provides the confidence that restoration of critical systems and data can be successfully completed when needed. As technologies and recovery procedures evolve, testing gives organizations the assurance that their disaster recovery strategies remain current and effective.
Virtualization
Virtualization can play a critical role in disaster recovery strategies by enabling faster recovery times. By leveraging virtualization software, businesses can minimize downtime in the event of a disaster by failing over to virtual machines hosted on secondary sites or in the cloud (Source). This approach, known as virtual disaster recovery, typically involves replicating virtual machine images to an alternate location so they can be quickly brought online if the primary location fails.
A key benefit of using virtualization for disaster recovery is the ability to replicate entire virtual environments. This eliminates the lengthy process of restoring data from traditional backups. Virtual recovery can also facilitate more frequent testing of DR plans through simulated failovers (Source). Overall, virtualization enables faster and more flexible recovery, minimizing downtime and data loss in the event of a disaster.
High Availability
High availability refers to systems that are designed to operate continuously without interruption to service. High availability is critical for database systems where downtime can be hugely detrimental.
A common high availability option for databases is clustering. Clustering involves having multiple database server instances spread across different nodes, with the data replicated across the nodes. If one node fails, the other nodes can continue operating and serving data without downtime. Clustering also allows for load balancing across the nodes.
Some popular database clustering solutions include Oracle Real Application Clusters (RAC), MySQL Cluster, and Microsoft SQL Server AlwaysOn Availability Groups. These provide automatic failover capabilities to keep the database operational in case of node failures.[1][2]
Other high availability features include redundant components like RAID disk arrays to handle disk failures, dual power supplies, and network interface card teaming. The goal is to remove single points of failure. High availability systems aim for maximum possible uptime and fast recovery time when problems do occur.
Setting up robust monitoring and alerting is also important to promptly detect issues and trigger failovers. Regular testing and reviews ensure high availability mechanisms function properly.
[1] https://www.scylladb.com/glossary/high-availability-database/
[2] https://aerospike.com/glossary/high-availability-database/
Conclusion
Database disaster recovery strategies are critical components of any comprehensive data protection plan. The key takeaways include:
- Prevention through security controls, access management, and change management processes can mitigate many risks.
- Leveraging real-time data replication, frequent backups, and secondary failover sites provides resilience against outages.
- Emergency response procedures should be documented and tested to ensure rapid restoration.
- New technologies like virtualization and high availability systems can enhance reliability and reduce recovery time.
- A multi-faceted disaster recovery strategy is recommended, combining preventative and reactive measures for optimal data protection.
By carefully implementing a combination of these database disaster recovery strategies, organizations can gain confidence their critical data remains readily available and minimize disruption in the event of unexpected failures or outages.