Disaster Recovery

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  1. Disaster Recovery

Introduction

Disaster Recovery (DR) is a comprehensive set of policies, procedures, and technical capabilities designed to enable the restoration of IT infrastructure and operations following a disruptive event. A disruptive event can range from natural disasters like earthquakes, floods, and hurricanes, to human-caused incidents like cyberattacks, hardware failures, or even accidental data deletion. Effective DR planning isn’t merely about *if* you can recover, but *how quickly* and with *how much data loss* (Recovery Time Objective (RTO) and Recovery Point Objective (RPO), explained later). For a wiki, which relies heavily on its database and underlying server infrastructure, a robust DR plan is absolutely critical to maintain accessibility and prevent irreversible data loss. This article will provide a detailed overview of disaster recovery principles, strategies, implementation steps, and best practices, tailored for MediaWiki administrators and those responsible for managing wiki environments.

Understanding the Risks

Before diving into solutions, it's vital to identify and assess the potential threats. For a MediaWiki installation, these risks can be categorized:

  • **Natural Disasters:** Fires, floods, earthquakes, hurricanes, and other natural events can physically damage servers and network infrastructure. Consider the geographic location of your hosting environment and the associated risks.
  • **Hardware Failures:** Hard drives crash, servers malfunction, and network devices fail. While redundancy (RAID, redundant power supplies) can mitigate some of these risks, they don't eliminate them entirely. Server administration is key to predicting and managing this.
  • **Software Failures:** Bugs in the operating system, database software, or MediaWiki itself can lead to data corruption or system crashes. Regular updates and testing are crucial.
  • **Human Error:** Accidental deletion of files, incorrect configuration changes, or security breaches caused by human negligence are common occurrences. Strong access controls and change management procedures are essential.
  • **Cyberattacks:** Malware, ransomware, Distributed Denial-of-Service (DDoS) attacks, and other cyber threats can compromise system integrity and data availability. A comprehensive security policy is paramount.
  • **Data Corruption:** This can occur due to hardware failures, software bugs, or even power outages. Regular database backups and integrity checks are vital.
  • **Loss of Internet Connectivity:** While not a "disaster" in the same sense as a fire, prolonged internet outages can render a wiki inaccessible, effectively acting as a disruption.

Key Concepts: RTO and RPO

Two fundamental metrics define the effectiveness of a disaster recovery plan:

  • **Recovery Time Objective (RTO):** The maximum acceptable duration of time that an IT system can be unavailable after a disaster. For example, an RTO of 4 hours means the wiki must be back online within 4 hours of the disaster occurring. Lower RTOs generally require more expensive and complex DR solutions. Consider the impact of downtime on your users and the wiki's purpose.
  • **Recovery Point Objective (RPO):** The maximum acceptable amount of data loss, measured in time. An RPO of 1 hour means you can tolerate losing up to 1 hour of data changes. Lower RPOs require more frequent backups. The importance of minimal data loss depends on the frequency of content updates and the sensitivity of the information stored on the wiki.

Understanding and defining these objectives is the *first* step in designing a DR plan. They drive the choice of technologies and strategies.

Disaster Recovery Strategies

Several strategies can be employed, each with different costs and levels of complexity:

  • **Backup and Restore:** The most basic strategy involves regularly backing up the MediaWiki database (MySQL/MariaDB or PostgreSQL) and the wiki's files (images, extensions, skins). In the event of a disaster, the data is restored to a new server. This is relatively inexpensive but has the highest RTO and RPO. Tools like `mysqldump`, `mariadb-dump`, `pg_dump`, and `rsync` are commonly used. See Database backups for detailed instructions.
  • **Warm Standby:** A warm standby site maintains a secondary server that is kept up-to-date with replicated data. However, the standby server is *not* actively serving traffic. In a disaster, the standby server is activated and brought online. This offers a lower RTO than backup and restore, but still involves some downtime. Database replication (MySQL replication, PostgreSQL replication) is a key component of this strategy.
  • **Hot Standby:** A hot standby site is a fully functional replica of the production environment, constantly synchronized with the primary site. In a disaster, traffic is automatically switched to the standby site, minimizing downtime. This offers the lowest RTO but is the most expensive and complex to implement. Load balancing and failover mechanisms are essential.
  • **Cloud-Based Disaster Recovery:** Leveraging cloud services (AWS, Azure, Google Cloud) provides a flexible and scalable DR solution. You can replicate your MediaWiki environment to the cloud and quickly spin up a new instance in the event of a disaster. This offers a good balance of cost and RTO/RPO. Services like AWS CloudEndure Disaster Recovery, Azure Site Recovery, and Google Cloud Disaster Recovery are available.
  • **Pilot Light:** A minimal version of your MediaWiki installation is kept running in the cloud. It's not serving live traffic, but it contains the core components needed to quickly restore functionality. Data is replicated regularly. This is less expensive than hot standby but offers a faster recovery than backup and restore.
  • **Multi-Region Deployment:** Deploying your MediaWiki installation across multiple geographic regions ensures that a disaster in one region will not bring down the entire wiki. This requires careful planning and synchronization of data.

Implementing a Disaster Recovery Plan for MediaWiki

Here's a step-by-step guide to implementing a DR plan for your MediaWiki installation:

1. **Risk Assessment:** Identify potential threats and their likelihood. Prioritize based on impact and probability. 2. **Define RTO and RPO:** Determine acceptable downtime and data loss levels for your wiki. 3. **Choose a DR Strategy:** Select the strategy that best aligns with your RTO/RPO requirements and budget. 4. **Backup Procedures:** 

   * **Database Backups:** Implement a regular backup schedule for your MediaWiki database.  Automate this process using cron jobs or scheduling tools.  Store backups offsite. Consider incremental backups to reduce storage space and backup time.
   * **File Backups:** Back up the `images/` directory, extensions, skins, and other important files.  Use `rsync` or other file synchronization tools.
   * **Configuration Backups:** Back up your `LocalSettings.php` file and other configuration files.

5. **Replication (if using Warm/Hot Standby):** Configure database replication to synchronize data between the primary and standby servers. Monitor replication status regularly. 6. **Failover Mechanism (if using Hot Standby):** Implement a load balancer and failover mechanism to automatically switch traffic to the standby site in the event of a disaster. Tools like HAProxy, Nginx, or cloud-based load balancers can be used. 7. **Documentation:** Create detailed documentation outlining the DR plan, including procedures for backup, restoration, failover, and communication. 8. **Testing:** Regularly test the DR plan to ensure it works as expected. Simulate disaster scenarios and verify that you can restore the wiki within the defined RTO and RPO. This is crucial. A plan that isn't tested is a plan that will likely fail. 9. **Monitoring:** Continuously monitor the health of your systems and backups. Set up alerts to notify you of any issues. 10. **Regular Review and Updates:** Review and update the DR plan periodically to reflect changes in your infrastructure, applications, and business requirements.

Technical Considerations

  • **Database Choice:** The choice of database (MySQL/MariaDB vs. PostgreSQL) can influence DR options. Both databases offer robust replication capabilities.
  • **Storage:** Consider using redundant storage solutions (RAID, SAN) to protect against hardware failures.
  • **Networking:** Ensure you have redundant network connections and a reliable internet service provider. Consider using a Content Delivery Network (CDN) to improve performance and availability.
  • **Virtualization:** Virtualization technologies (VMware, KVM, Xen) make it easier to create and manage backups and replicas.
  • **Containerization:** Containerization technologies (Docker, Kubernetes) can simplify DR by packaging your MediaWiki environment into portable containers.
  • **Automation:** Automate as much of the DR process as possible to reduce errors and improve efficiency. Tools like Ansible, Puppet, and Chef can be used for automation.

Best Practices

  • **Offsite Backups:** Store backups in a physically separate location from the primary site.
  • **Version Control:** Use version control (Git) to track changes to your configuration files and code.
  • **Principle of Least Privilege:** Grant users only the permissions they need.
  • **Security Hardening:** Secure your systems against cyber threats.
  • **Regular Security Audits:** Conduct regular security audits to identify and address vulnerabilities.
  • **Change Management:** Implement a formal change management process to control changes to your infrastructure and applications.
  • **Documentation is King:** Maintain comprehensive documentation of your DR plan and procedures.
  • **Continuous Improvement:** Continuously review and improve your DR plan based on lessons learned from testing and real-world events.
  • **Consider a Disaster Recovery as a Service (DRaaS) provider:** For smaller organizations, a DRaaS provider can offer a cost-effective and reliable DR solution.

Indicators and Trends in Disaster Recovery


Server security Database administration Wiki maintenance Security policy Backup strategies Network configuration System administration Data recovery Load balancing Content management

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